Planecrazy, do not have lasik surgery, having a + in front of your prescription limits lasik surgery to a maximum of +3 in order to guarentee results.
Some other lasik providers might give you the go ahead, but they will be in your eyes for the money not for your benefit.
Intra-ocular lenses are a very good solution that not everyone suits, you need to go through a few tests to measure the space available in between retina and cornea, different prescriptions need more space than others, being longsighted is one of them, so no ophtalmologist can say that you can have intra-oculars before this tests are done.
By the way, the CAA might not be very happy about surgery as you are not within limits for Class I initial.
Do not bother to get a different prescription somewhere else, if you ever make it to Gatwick for the initial class 1, you will have a proper one done over there, and in your case that is the one that counts.