Can any one on the BBS tell where I can get my big nikko serviced?

I was finding that my shots were dropping from 40 yards and over intermittently, first thought was that my gun was dropping power but a batch of 40 or so pellets through the crono found that its spot on with no problems. I think that my scope which I've had now for 3/4 years is the problem and probably has something sticking.

Finally managed to get the tel number for Nikko (Highland Outdoors in Leicester area?!?!?!) and they have no idea where I can get it serviced but can sell me a new one?!?!?!?!?

Anyone on here know of a good place to get it serviced?