there are loads to choose from in Kent.The ones that spring to mind are Saddleworld based in Maidstone who have their own website,Michael Uden Stowting based I think,and Saddle rack based at Hawkinge.It depends where you are based in Kent.
Bridlepath International travel (don't know if they do Kent). Very good. Recommended to me and I've recommended them to others and so far all happy bunnies.