I have worse values than this (exophoria actually) and hold a class 2, but am outside the limits for class 1 (also on dioptre correction).
The CAA would normally advise you if you send them a copy of the optometrists report, without having to do the full medical first.
I think that prism correcting glasses would take a long time to get used to, I was advised that they wouldn't really help as the brain has already learnt to cope with the imbalance.