Why don't you print of the eye sight requirements from the CAA website under "Medical". Take these to your local eye testing centre (Specsavers, Vision Express etc etc) and pay the £22 to have them tested against those specifications.
If they throw up any problem then you can give the CAA medical team a ring and throw the science at them of what was found. If you are given the all clear, then great, you can go to Gatwick with a lot less worry on your shoulders.