NutLoose
Re your note about the 'twin engine Cirrus' comment a few posts (and years) back. I saw the same thing when going through the Part-M Subpart F/G(I) saga.
At the time we were told we could only have on our approval, types for which we held current airworthiness data. I therefore requested (in writing) that we put Captain Scarlet's Angel Interceptors on our approval as I was sure there was more maintenance data available than for a Cirrus twin....
My understanding on the Cessna seat belt issue (comes up every CAA engineering seminar) was that if you could justify not doing them to the authority with a sound reason then that would be acceptable. A 10 year old privately owned, hangared, aircraft is unlikely to have belts suffering the same as a club hack that lives out doors in the sun and rain.
As you say, jxk, what a judge would say if there was ever a fatal involving insurance/compensation claims it would be a difficult case - especially for the engineer/organisation involved.
I do believe that there is a company in Scandanavia who can re-web Cessna seat belts and issue an EASA Form One for the work.