I thought an imobiliser had to be done as part of compliance as well... I know it was on my car same with the freqency expander.
With the compliance workshops, there is also the double edgded sword...
If they do it properly, they replace all the fluids, change the brakes, rip out your Xenons, cut up your exhaust to fix a new cat, fit the cheapest tyres they can find etc...
With my R33 it was less of an issue.. no Xenons, cat is a bolt in, nice cheap tyres on 16" rims..
With my M35, was really glad they were half hearted in some areas but official in others... Xenons were stil there, as was the stock front pipe and cats, not like Cam's Frankenexhaust.. They had changed the cabin filter, engine oil and brake pads, but not the air filter or the quality Japanese 18" tyres. Seat belt tethers were really well installed, which is important given the two child seats in the car..
I bought both my cars from the places that actually did the compliance. That did give me a bit of faith as well as access to parts when I needed them, during the first 3 month warrantys, new speedo for the R33, tie rod end on the M35, with no questions or hassle.
The reallity is, that once you get that car parked out the front of the house... You don't care any more... It's there and it's yours...