There are very very few TB200s anywhere, especially in the UK.
But it is just a TB10 (essentially) with fuel injection and 20HP extra.
My suggestion is to do your own 50hr checks, accompanied by an engineer for the less trivial bits of the job (and the lower cowling is a 2-man job anyway). That will ensure the work is done well, and will save you loads of £££.
Then find a company familiar with TB20s. They ought to do an Annual for ~£2000, but you will need to pay them a few hundred extra to actually do the stuff that should be done i.e. proper greasing (NOT spray "lube" which is what most firms do) of control linkages etc. That ought to do it. Having fixed gear saves you maybe £300 on the Annual, over a TB20.
TBs are very easy to work on.
I have owned a TB20GT since new in 2002.