Really depends how much money you want to spend. Ally Brown (team chase rider for Hairraisers) is amazing at bringing on and schooling horses. She owns Argae House stables, just outside of Cardiff.
My sister owns a livery yard/riding school/breaking schooling in the Vale of Glamorgan.
Her riding instructor/groom Jade was 'young instructor of the year' last year, the yard is professional, clean and tidy with a nice friendly atmosphere and is incredibly well equipped.
Have a look at her website and just give her a call for a chat, if you are interested...