I wanted to share data between a SwiftUI view (and its viewmodel) and a SpriteView.. specifically I wanted the SwiftUI view to see the touch co-ordinates of the SpriteView and update them in the interface and for a Button to update the position of a target in the SpriteView.. I'd been unable to find any solutions online, but quite a few people asking similar questions to me. Here's my solution.. (I'm a noob so please excuse the code, and if there are better ways of doing things please let me know!

ContentView:

import SwiftUI
import SpriteKit

struct ContentView: View {
    @StateObject var contentViewModel = ContentViewModel()
    @State private var pan: CGFloat = 0
    @State private var tilt: CGFloat = 0

//    var scene: SKScene {
//        let scene = TargetScene()
//        scene.size = CGSize(width: 500, height: 300)
//        scene.scaleMode = .fill
//        contentViewModel.currentTargetScene = scene as TargetScene
//        return scene
//    }

    var body: some View {
        ZStack {
            Text("This is the view underneath: ")
                .offset(CGSize(width: 0, height: -50))
            HStack {
                SpriteView(scene: contentViewModel.scene, options: [.allowsTransparency])
                .frame(width: 500, height: 300)
                    .ignoresSafeArea()
                    .border(Color.blue)
                VStack {
                    Spacer()
                    Button("Reset to centre") {
                        contentViewModel.moveToCentre()
                    }
                    .padding()
                    Button("move to co-ords ") {
                        contentViewModel.moveToLocation()
                    }
                    .padding()
                    Button("get location") {
                        contentViewModel.getLocation()
                    }
                    .padding()
                    Text("Pan: \(pan)")
                    Text("Tilt: \(tilt)")

                    Spacer()
                }
                .onReceive(contentViewModel.currentTargetScene!.pointPublisher, perform: { target in
                    pan = target.x
                    tilt = target.y
                    contentViewModel.pan = target.x
                    contentViewModel.tilt = target.y
                })
            }
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

ContentViewModel:

import Combine
import Foundation
import SpriteKit

class ContentViewModel: ObservableObject {

    var currentTargetScene: TargetScene?
    var targetPosition = CGPoint(x: 0, y: 0)
    var scene: SKScene

    init(){
            scene = TargetScene()
            scene.size = CGSize(width: 500, height: 300)
            scene.scaleMode = .fill

            currentTargetScene = scene as? TargetScene
        }

    @Published var pan: CGFloat = 0
    @Published var tilt: CGFloat = 0

    func moveToCentre() {
        // move target to centre of SpriteView
        currentTargetScene?.moveToCentre()
    }

    func getLocation() {
       //  update ContentView with the target's x + y coordinates
        targetPosition = currentTargetScene?.targetPosition ?? targetPosition
        pan = targetPosition.x
        tilt = targetPosition.y
        print(targetPosition)

    }
    func moveToLocation() {
        currentTargetScene?.moveToLocation(x: 100, y:100)
    }
}

TargetScene:

import Foundation
import SpriteKit
import Combine

class TargetScene: SKScene, ObservableObject {

    weak var contentViewModel: ContentViewModel?

    var lastUpdateTime: TimeInterval = 0
    var dt:TimeInterval = 0

    let image = SKSpriteNode(imageNamed: "Target.png")
    let imageSize = CGSize(width: 100, height: 100)

    let targetMovePointsPerSec: CGFloat = 500.0
    var velocity = CGPoint.zero
    var lastTouchLocation: CGPoint?

    @Published var pan: CGFloat = 0 {
        didSet {
            pointPublisher.send(CGPoint(x: self.pan, y: self.tilt))
        }
    }
    var tilt: CGFloat = 0 {
        didSet {
            pointPublisher.send(CGPoint(x: self.pan, y: self.tilt))
        }
    }

    @Published var targetPosition = CGPoint(x: 0, y: 0)

    public let pointPublisher = CurrentValueSubject<CGPoint, Never>(CGPoint(x: 0, y: 0))
    private var cancellableSet = Set<AnyCancellable>()

    override init() {
        super.init(size: CGSize(width: 500, height: 300))

        pointPublisher
            .sink(receiveValue: { [unowned self] target in
                self.targetPosition = target
            })
            .store(in: &cancellableSet)

    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func didMove(to view: SKView) {
            physicsBody = SKPhysicsBody(edgeLoopFrom: frame)
        image.position = CGPoint(x: 0, y: 0)
        image.scale(to: imageSize)
        addChild(image)
        }

    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {

        guard let touch = touches.first else { return }
        let location = touch.location(in: self)
//        print(location)
        pan = location.x
        tilt = location.y
        lastTouchLocation = location
        moveTargetTowards(location: location)
        updateLocation()
    }

    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
        guard let touch = touches.first else { return }
        let location = touch.location(in: self)
//        print(location)
        pan = location.x
        tilt = location.y
        lastTouchLocation = location
        moveTargetTowards(location: location)
        updateLocation()
    }

    override func sceneDidLoad() {
        scene?.anchorPoint = CGPoint(x: 0.5, y: 0.5)
        let backgroundColor: UIColor = UIColor(white: 0, alpha: 0.3)
        scene?.backgroundColor = backgroundColor

    }

    override func update(_ currentTime: TimeInterval) {
        if lastUpdateTime > 0 {
            dt = currentTime - lastUpdateTime
        } else {
            dt = 0
        }
        lastUpdateTime = currentTime

        //To move sprite in a direction
     //   moveTarget(sprite: image, velocity: CGPoint(x: targetMovePointsPerSec, y: 0))

        if let lastTouchLocation = lastTouchLocation {
            let diff = lastTouchLocation - image.position
            if (sqrt(diff.x * diff.x + diff.y * diff.y) <= targetMovePointsPerSec * CGFloat(dt)) {
                image.position = lastTouchLocation
                velocity = CGPoint.zero
            } else {
                moveTarget(sprite: image, velocity: velocity)
            }
        }
    }

    func moveTarget(sprite: SKNode, velocity: CGPoint) {
        let amountToMove = CGPoint(x: velocity.x * CGFloat(dt), y: velocity.y * CGFloat(dt))

        sprite.position = CGPoint(x: sprite.position.x + amountToMove.x, y: sprite.position.y + amountToMove.y)
    }

    func moveTargetTowards(location: CGPoint) {
        let offset = CGPoint(x: location.x - image.position.x, y: location.y - image.position.y)
        let length = sqrt(Double(offset.x * offset.x + offset.y * offset.y))
        let direction = CGPoint(x: offset.x / CGFloat(length), y: offset.y / CGFloat(length))

        velocity = CGPoint(x: direction.x * targetMovePointsPerSec, y: direction.y * targetMovePointsPerSec)

    }

    func moveToCentre() {
        let actionMove = SKAction.move(to: CGPoint(x: 0, y: 0), duration: 0.5)
        image.run(actionMove)
        self.pan = 0
        self.tilt = 0
        updateLocation()
    }

    func updateLocation() {

    }

    func moveToLocation(x: CGFloat, y: CGFloat) {
        let actionMove = SKAction.move(to: CGPoint(x: x, y: y), duration: 0.5)
        image.run(actionMove)
        self.pan = x
        self.tilt = y
        updateLocation()
    }

}

Hope this helps someone else out there!