Wahey, it's fixed!! I pulled everything off the drivers seat that I could and got my wife to hold the seat belt buckle still while I moved the seat backwards and forwards. Guess what? The rattle was still there!! Damn! So, I laid down in the footwell behind the seat and got the wife to move the seat backwards and forwards and just by chance, I spotted a pound coin had fallen between the frame on the seat and the runners attached to the floor. When I say fallen, I suspect it had been pushed in by a child of the previous owners because there was no way it could fall in. So, rattle gone and I'm a pound up on the deal!!