Where are you based?
These ought to give you an idea whats near one another, and just how far away some of them are:
Welsh Trail centres without purpose-built facilities
Welsh trail centres with purpose-built facilities
guide to scottish trail centres (not FC)[/url]
Can’t find anything comprehensive on england but apparantly this is the lot for the UK:
England
Aston Hill
Bedgebury
Cannock Chase
Chicksands
Dalby
Delamere
Forest of Dean
Friston Forest
Gisburn
Grizedale
Guisborough
Haldon
Hamsterley
Hopton Wood
Kielder
Queen Elizabeth Country Park
Rossendale Lee Quarry
Sherwood Pines
Stainburn
Surrey Hills
Swinley Forest
Thetford Forest
Timberland Trail
Wharncliffe
Whinlatter Forest
Scotland
Abriachan
Ae
Arran
Balblair
Carbisdale
Carron Valley
Comrie Croft
Dalbeattie
Drumlanrig
Fire Tower Trail
Fort William
Glentress
Glentrool
Golspie
Innerleithen
Jedburgh
Kirkhill
Kirroughtree
Laggan
Learnie
Mabie
Moray
Mull of Kintyre
Newcastleton
Pitfichie
Strathpeffer
Wales
Afan Argoed
Brechfa
Cli-machx
Coed Llandegla
Coed Trallwm
Coed y Brenin
Cwmcarm
Cwm Rhaeadr
Gwydyr Forest
Mach Trails
Nant yr Arian
Penmachno
Bike Parks
Balnain
Blandford Forum – UK Bike Park
Esher
P.O.R.C.