You're in the Wild West which might mean Devon or it might mean the Hebrides. If the former there is Jon French at Staverton or if the Hebrides, John Maher, Isle of Harris.
Who's best? I'd say probably the latter. There will be others, I'm sure.
Cost? Who knows, and it'll probably depend on how much work is required, but you're probably looking at two - three grand as a minimum.
I'm presuming your prop is wood so on that assumption I'd guess the crank is OK, but as a starter you could put a dial gauge on the prop hub front face at it's diameter and check runout.
Runout numbers for the Rectimo VW conversion are:
Greater than 0.09 mm, replace the prop hub.
Re-measure the run-out and if still higher than 0.04 mm, then the crank is suspect and should be checked.