Welcome!!
Im in surrey... pls dont bother servicing in Nissan dealerships unless u really want the Nissan Stamp (bit better when its time for re-sale), Nissan dealers in surrey are extremely expensive and are not particularly knowledgeable about our Z's (id only take a Micra/Primera to them hehe)
Go to a performance garage like Abbey Motorsport (Grimstead) or use a reputable place like Evans (in Epsom), they did my car few weeks ago and im v pleased....better price and better service!! At the very least theyll use the best performance oil for our application and theyll do any extras u need on the side.