It would seem that if Acft has MTW > 2730kg then any Tests must be done from Licensed Aerodrome.
That's not quite correct as it is not
any test under ANO Art 208, but a test MTWA >2730kg which is for the purpose of becoming qualified for a licence or rating, i.e. a skill test.
A proficiency check is conducted to renew or revalidate a rating, and does not require a licensed airfield.
EASA FCL.010 Definitions
‘Proficiency check’ means the demonstration of skill to revalidate or renew ratings, and including such oral examination as may be required.
...
‘Skill test’ means the demonstration of skill for a licence or rating issue, including such oral examination as may be required.