Looking on their website... if someone like their Senior Organ Scholar James Kealey is on offer... I would definitely go for him.
I have sung in Wells Cathedral but not played there... lovely place for a wedding!
If the cathedral offer an organ scholar - I would bite their hand off personally. If they want to spend money on a top end recitalist - I can put you in touch with two of the country's finest.
I have be known to play the organ on occasions and in the odd cathedral, but perhaps for the end of the market you seem to be looking, I do have connections with several professional organists... not sure what sort of fees we are talking but I am happy to put you in touch. Which cathedral is it...