I use ACspeedtech, awesome guys there, great service and brilliantly prices! Give Andy a shout.
I spoke to SVM and litchfield as well whilst I was investigating who to do the work.
+1 on acspeedtech as well, always been very helpful to me, and really know their stuff, and they go the extra mile to get your car sorted, top guys.I've had my GTR less than a week and used AC Speedtech for some tuning work at the weekend....
Andy is great and they were very well priced for the work they carried out and for the jobs I have planned in the future!