Car seat. If I put a spirit level across the drivers seat the bubble dips 15% degrees to one

Question

If I put a spirit level across the drivers seat the bubble dips 15% degrees to one side. This makes for uncomfortable driving (the back and hip joints are out of alignment). Where can I get the seat reupholstered in Kent ? If possible, somewhere that will remove the seat and replace one fixed (carrying the seat from one place to another is not practical - since I won't have a car (Mercedes E Class ). Many thanks.