Here are some links you may find useful:

 

https://www.bhs.org.uk/Riding/British_Riding_Clubs.aspx

http://www.brcarea22.com/

http://www.britishdressage.co.uk/ 

http://www.Flashhorse.com

http://www.gilwaunwesternridingranch.com

http://www.grasssickness.org.uk

http://www.icehorses.co.uk

http://www.pammillardressage.com

http://www.scottishcarriagedriving.com