SB19,
It is indeed true that the CAA seem to look favourable on people with experience and class1 medicals by another ICAO state.
The scenario is usually one whereby the person has got say an FAA CPL or ATPL and now needs a class1 for a JAR licence.
Not sure if the same would work if you are just getting a class1 medical.
The FAA is indeed only interested (refraction wise) in a good corrected vision, so it does not matter how strong your prescription is.
There are a fair few FAA AMEs (and one more at that since early this month
)in the UK but not sure if there is one in Devon.
However
here is a list so you can check that out yourself.
I see what Jinkster is saying but think you need to talk to the CAA first before you have any refractive surgery done. They are very conservative when it comes to that. Some techniques are better than others but long term complications are possible and can endanger your ability to achieve any class of medical.
Let us know how you get on.
Good luck,
FD