Lee, I used to live in Newquay so just up the road from Perranporth, give Newquay BSAC a bell, they used to have regular mid week dips with space for visitors and there is also a new shop there that runs trips here
http://www.divenewquay.co.uk/index2.html ,a mate uses them and has good words about the outfit.
or Cornish divers in Falmouth have always looked after me. Try this site for some gen as a start til some of the current locals get back to you.
http://www.divingcornwall.com/
Pez