Alistair's advice is spot on.
What you are describing would seem to be the system loosing pressure; however, if it was recently repaired, you would hope the mechanic had pressure tested the system.
There are no common faults with the A/C system on Morgan Aero 8s; therefore, it will be difficult for anyone to guide you past what has been said above.
I would suggest that you speak with your closest Morgan repair agent and failing that, call the factory direct (speak with the repair shop) and explain that you are calling from the USA and would like advice on the possible solution to the issue.
