The waves vary so much in Cornwall, one day it could be fun for longboarding, the next you need a short board, then a fish. It really is that changeable, so it is wise to have a bit of a quiver if can afford it.
Boards are easily available, places like Newquay have loads of shapers and surf shops so getting a new or second hand one is easy. They are not particularly cheap though and it pays to shop around for a deal, but it’s always good to try and support local shapers.