Sorry to hear of your engine problems, that is exactly what happened to me, lights included. I think that as the tensioner blade comes apart the hydraulic tensioner comes out of its location and loses all the oil pressure but thats water under the bridge. I had mine done by an Indy in Tyneside, but he shouldnt even work on a push bike so he is no use to you. I ended up stripping the engine myself. (My V8 Engine Rebuild)
As you are in the South of the UK, this UK based website might also help you with a local garage, plenty of members are from down there. There are a lot of threads on Xoutpost about the same problem as it is common with this engine.

I doubt you will find a good engine in the UK, as they are very rare, I tried when mine blew. Unlike the US, I couldnt find any stockists of pattern parts for this engine so had to use BMW spares. Cost 3 grand for the original 'repair', and another 3 grand when I did it properly. You will need a large garage if you want to take the engine out, but the camchains are possible in the street. If you need any info about what you need, PM me