FL 390
The eyesight regulations are a much talked about topic within the RAF and indeed the UAS.
You mention wearing glasses. Looking at past applicants I know of I'd say there isn't really much chance of being accepted by the RAF as a pilot.
I don't think you have to have "perfect" vision but I do know they are very strict with the medical guidelines.
You might want to contact OASC for a better answer.
TK