When I bought my Pro Target it was leaking through the little hole in the reg so I stripped it down to action and reg (cos I couldn't get the reg unscrewed!) and sent it off to air arms.
They completely stripped and rebuilt and set the reg using harder seals and it has been perfect ever since.
This was about a year ago but they only charged £42 and that included sending it back by courier. I sent it on a Friday and it was all done by the following Tuesday.
They designed and built it and they don't charge a fortune to service it.
Why bother sending it anywhere else?