Any ideas as to why I get this error please ?

You missed a closing bracket on the first FixedUpdate(). You also have FixedUpdate() twice which I think is not possible, unless you meant that to be Update().

Sure, Your FixedUpdate function is missing it's closing bracket. So the compiler sees that you declared your Start function inside another function but that's not possible.

Next thing is you have two FixedUpdate functions. That's also not possible. just merge them into one by taking the content of one of them and paste it inside the other.

Btw, what's the point of merging two scripts? The great thing about components is that you can keep them simple and just attach them to the object you want. If they do different things, keep them seperated, but that's up to you.

 using UnityEngine;
 using System.Collections;
 
 public class CarCamera : MonoBehaviour
 {
     public Transform target = null;
     public float height = 1f;
     public float positionDamping = 3f;
     public float velocityDamping = 3;
     public float distance = 50f;
     public LayerMask ignoreLayers = -1;
 
     private RaycastHit hit = new RaycastHit();
 
     private Vector3 prevVelocity = Vector3.zero;
     private LayerMask raycastLayers = -1;
     
     private Vector3 currentVelocity = Vector3.zero;
     
     
     private float bumperDistanceCheck = 2.5f; // length of bumper ray
   private float bumperCameraHeight = 1.0f; // adjust camera height while bumping
  private float damping = 5.0f;
     private Vector3 bumperRayOffset; // allows offset of the bumper ray from target origin
  
     private Vector3 targetLookAtOffset; // allows offsetting of camera lookAt, very useful for low bumper heights
     
     private bool smoothRotation = true;
     
     private float rotationDamping = 10.0f;
  
     
     
     
     void Start()
     {
         raycastLayers = ~ignoreLayers;
     }
 
     void FixedUpdate()
     {
         currentVelocity = Vector3.Lerp(prevVelocity, target.root.rigidbody.velocity, velocityDamping * Time.deltaTime);
         currentVelocity.y = 0;
         prevVelocity = currentVelocity;
            
         Vector3 wantedPosition = target.TransformPoint(0, height, -distance);
  
         // check to see if there is anything behind the target
         RaycastHit hit;
         Vector3 back = target.transform.TransformDirection(-1 * Vector3.forward); 
  
         // cast the bumper ray out from rear and check to see if there is anything behind
         if (Physics.Raycast(target.TransformPoint(bumperRayOffset), back, out hit, bumperDistanceCheck)
             && hit.transform != target) // ignore ray-casts that hit the user. DR
         {
             // clamp wanted position to hit position
             wantedPosition.x = hit.point.x;
             wantedPosition.z = hit.point.z;
             wantedPosition.y = Mathf.Lerp(hit.point.y + bumperCameraHeight, wantedPosition.y, Time.deltaTime * damping);
         } 
  
         transform.position = Vector3.Lerp(transform.position, wantedPosition, Time.deltaTime * damping);
  
         Vector3 lookPosition = target.TransformPoint(targetLookAtOffset);
  
         if (smoothRotation)
         {
             Quaternion wantedRotation = Quaternion.LookRotation(lookPosition - transform.position, target.up);
             transform.rotation = Quaternion.Slerp(transform.rotation, wantedRotation, Time.deltaTime * rotationDamping);
         } 
         else 
             transform.rotation = Quaternion.LookRotation(lookPosition - transform.position, target.up);
     }
 
     
     void LateUpdate()
     {
             
         
         float speedFactor = Mathf.Clamp01(target.root.rigidbody.velocity.magnitude / 170.0f);
         camera.fieldOfView = Mathf.Lerp(55, 72, speedFactor);
         float currentDistance = Mathf.Lerp(45.5f, 6.5f, speedFactor);
         
         currentVelocity = currentVelocity.normalized;
         
         Vector3 newTargetPosition = target.position + Vector3.up * height;
         Vector3 newPosition = newTargetPosition - (currentVelocity * currentDistance);
         newPosition.y = newTargetPosition.y;
         
         Vector3 targetDirection = newPosition - newTargetPosition;
         if(Physics.Raycast(newTargetPosition, targetDirection, out hit, currentDistance, raycastLayers))
             newPosition = hit.point;
         
         transform.position = newPosition;
         transform.LookAt(newTargetPosition);
                 
         
         }
 }

heres my mix up of the two scripts but i am totally losing the terrain collison thing now :)