I levelled ours as I went, really you want to be using the powdered mix at home adhesive as it sets quicker and gives a better result if laid thicker than normal.
Not bad to do once you get cracking.
When I fitted our bath I made sure to leave good access for taps, waste and pipes, seems others do the exact opposite and end up with what the OP is dealing with.
If you keep your vehicle in good order and serviced you should have no bother at MOT time.
We've seen some absolute death traps over the years, should not have been on the road.
I bought a Petrol leaf vacuum last year and to say the choke diagram was ambiguous was ab understatement. Why can they just print on and off next to the bloomin thing!.
Old Lambretta's and Vespa PX's have spilt rims, and that's it.
Everything else has a one piece rim.
Even the PX owners buy a cast 1 piece alloy wheel as an "upgrade".