Live in mid Cornwall, and have run various golfs for a few years.
Depends on the "tuning" that you are looking for, of course....But not aware of anyone local. Guess we aare a very limited market?
Have you tried the SW Dubs web site?
As i work oooop North, My current ed 30 was tuned...mapped (APR), walk, poly bushed etc, at Awesome GTi in Irlam, Manchester.
Happy with them.
Dan at Devon dub shack (Plymouth) has done standard mechanical work for me on my mk3 cabby, & saloon hack (more of a skip really!) etc, happy with his work.