Kev,
access to results may be the issue here. While some GP surgeries send their bloods to the same hospital you attend for clinic, others use a different hospital. If that is the case, it is likely that neither can see the other's test results. In that case, you are back to the good old letter, typed up by a secretary and posted to the other team.
You may do better if you get the raw results from the clinic, visit your GP, explain the conflict between teams' advice and discuss the clinic's results and their reasons for putting you on Ramipril.
If they come across as superior, and knowing more than you, it's time for a second opinion!