Every year we change almost everything that is not original out. For me that is: front of the cage, seats, seatbelts, wheels, brakes, suspension. Then i got to the Mot and iff i'm lucky the wont see the engine " tuning" parts like intercooler or bigger exhaust, efi kit otherwise they have to be changed also. When they were doing the mot the guy claimed i had shorter ratios gearbox because he felt it while shifting the car. I had to explain him that this was because of the short shifter kit on the car and had nothing to do with the actual gearbox ratios. He was one of the better controllers and let it be otherwise the kit could had been removed to get the mot.
You guys in the uk have no idea how lucky you are.