The Glove, you need proper advice from your careers master or the AFCO.
The A-levels and type of degree you will need may be fairly specific and you will possibly not get best advice here.
As for engineering officers doing maintenance, I have no idea what gave you that idea. Engineering officers are certainly taught how to maintain engineering bits but they don't actually do that. Initially they supervise airmen who actually do the work. That supervision is more of an administrative nature than engineering.
Later there will be other openings but more in management than hands on oily stuff.
You should also try and join your local ATC Sqn.