In reply to kingjam:
You don't have to join the FRA, fell running isn't that exclusive! Might be worth lurking/asking on the FRA forums -
http://forum.fellrunner.org.uk/forum.php
The FRA do publish a list of races
http://fellrunner.org.uk/races.php but if you do join then you get a calendar and three magazines a year for the princely sum of £12. Races are categorised in two ways: by distance and by ascent/mile (toughness). Distances are: (S)hort, less than 6 miles; (M)edium, less than 12 miles & (L)ong. Toughness is indicated by A, B, C with A being the toughest. So a BM is a race between 6 & 12 miles in length with a moderate amount of up and down.
Basically find a race nearby, turn up, pay your money and run!
Races requiring good navigational skills have NS next to their details. Some of the longer, potentially more serious, races ask that you can demonstrate suitable fell running experience before you can enter.
Other than that, get out there and run!
ALC