Useful Links

CrossFit and Functional Fitness

CrossFit Main Site
CrossFit Kids
CrossFit Football
UK Strength and Power Series
GU1 Strength and Conditioning

Other Useful Resources

Catalyst Athletics
Everyday Paleo
Mark's Daily Apple
Growing Up Paleo
Krav Maga Guildford

UK and Ireland CrossFit Affiliates

CrossFit Optimus
AFS CrossFit
Britannia CrossFit
Capital CrossFit
Celtic CrossFit
Clan CrossFit
CrossFit 3D
CrossFit Avon
CrossFit Bath
CrossFit Ben Nevis
CrossFit Boat Shed
CrossFit Bold 
CrossFit Bristol
CrossFit Cardiff
CrossFit Carlisle
CrossFit Central London
CrossFit Central Manchester
CrossFit Clitheroe
CrossFit CM2
CrossFit Connect
CrossFit Cork

CrossFit Dental
CrossFit Dublin
CrossFit Essex
CrossFit Fareham 
CrossFit Fife
CrossFit Glasgow
CrossFit HG3
CrossFit Harrogate 
CrossFit Hove
CrossFit Intensity
CrossFit Ireland

CrossFit Leeds
CrossFit Liverpool
CrossFit London
CrossFit Mallow 
CrossFit Manchester
CrossFit Newcastle
CrossFit North East England
CrossFit Northampton
CrossFit Northern Ireland
CrossFit Plymouth
CrossFit Port Talbot 
CrossFit Reading
CrossFit Scotland
CrossFit Shropshire
CrossFit Surrey
CrossFit Swansea
CrossFit Tameside
CrossFit Tonbridge

CrossFit Tyneside
CrossFit Velocity
CrossFit Waterford 
CrossFit West Yorkshire
CrossFit Westcountry
CrossFit Wyre Forest
Dragon CrossFit
East Kent CrossFit 
Thames CrossFit

If I missed anyone just send me a mail and I will update the list.

CrossFitter Colin McNulty has created an excellent (and frequently updated) list and map of all the UK/Ireland affiliates. You can find it here