After having trouble getting anyone to quote for the repair (job must be too small to be of interest) I have decided to replace the adaptor and ridge tile myself then get the gas board back to smoke test.
My problem is that the new adaptors are all aluminium and I've been told that I need to get an asbestos to Selkirk adaptor, all I can find is a Selkirk 4 inch IL gas vent (which I've also been told is correct) and no supplier I've been to seems to have heard of the asbestos to selkirk adaptor, ANY ADVICE WOULD BE APPRECIATED