I think the CAA will actually issue Class 1 medicals to those who have had LASIK treatment, but only if the pre-corrective levels were within the specified limits. This condition makes corrective laser treatment useless if it's to achieve class 1 sight.
golf.charlie.foxtrot, I also have problems with my sight. Whilist I have 6/6 acuity, I have correction for astigmatism of -3.25 in one eye, so the CAA won't issue a Class 1.
You could try the FAA. Whilst they have the same sight standards (i.e corrected vision must 6/6) there is no limit on the level of correction. Assuming you can correct your sight to 6/6 you should be able to get an AME in the UK who is certified by the FAA to issue a Class 1 to you.
The only drawback with this is that you'd have to do any commercial flying on an American licence (or license), restricting you to either American registered aircraft or flying for airlines that do not stipulate which state your licence was issued in, as long as it's ICAO compliant. You wouldn't be able to fly for a UK airline.