P51,
How short sighted are you? The RAF do have marginal limits on eyesight (can anyone expand?!?) so in your shoes, i'd get my head in the books/RAF website and pull my finger out.
So far, even with duff eyesight, you could have got:
A 6th form flying scholarship (1/2 a ppl!)
You could be on a UAS, Ground Branch (eg short sighted) studes are allowed to fly a bit, but if you're keen, you can go to the airfield when it's quiet and get a bit more flying in.
If you're not too fussed about being an officer, you could go down the non commisionned aircrew route where there are loads of flying oppurtunities.
Have a think about whether you want to serve in HM forces and if you do then do your homework as to eliminate schoolboy questions and get down to your local careers office.
All the best!
GF
P.S. If you decide the RAFs not for you, my recommendation would be to stay out of the UAS as it is a large social and serious responsibility and isn't there for pure enjoyment.