Absolue best garage - Lockwood and Greenwood just off the M60 (jctn 23). They were a former Nissan dealer turned independent, and are very well recommended on the forum. I think you even get a discount if you mention the forum...
I got a P3 service done by them the other year, and i think it was either £190 or £230, i cant remember, but either way, a bargain.