There is no cheap way now.
The new shells get knocked all the time but they are good for what they are. £7k get you a basic shell that needs a lot of prep and altering to properly copy a ford shell.
Then your stuck for registering it. You can reshell a knacked shell but you will pay at least £2k for a load of scrap.
Or you can build a full new car and register it as new just like a kit car.
none of it is cheap.