Jab
Firstly - the requirements for the initial medical are not as stringent as those for the renewals so they take into account the fact that the eyes will deteriorate. I believe the renewal criteria is something like 5 dioptres - it's certainly more than the initial.
The NATS medical is more stringent than the CAA class one which is why there is a discrepancy with pilots.
Plenty of controllers wear glasses/contacts and have no problems whatsoever so don't worry about that. At 26 your eyes are going to be pretty settled so I would imagine you won't have any problems
