GAGB

There are a large amount of regional forums within the UK, below is  a collection of links to them:

Isle of Wight Geocaching Website for caching on the Isle of Wight
South Wales Geocachers The place to go for caching in South Wales (members only forum)
Yorkshire Geocachers Forum for Yorkshire caching
Geocaching Wales Geocaching forum for Wales
NW Geocaching Forum for caching in the North West
AberCachers Forum for caching and walking in Wales
SE Caching Forum for caching in the South East
EA Cachers East Anglia caching forum
Cache Walker The place to go for caching by Byeway  not Highway
EM Cache East Midlands caching forum  (members only section)
GeoFrees Caching forum for Scotland (members only forum)
GeoX Scotland & Ireland forum
Warwickshire Geocachers Website and Forum for the Warwickshire Geocaching Association
Kernow Kachers Forum for caching in Cornwall
Geocaching-Wales Another caching site for Wales
West Midlands Regional Geocaching A Forum for all Geocachers in West Midlands
Warrington Cachers Forum For people who cache in and around the Warrington area of North West England
GCAyrshire GeoCaching around Ayrshire
Dartmoor Caching Website and Forum for caching on Dartmoor