Mike if you like throwing money away just for a stamp in your service book then stick with the main dealer.
Personally I have found them less than satisfactory and at double the price of a good independent too.
For example: When I first got my 350 I had my local Nissan dealership supply & change my spark plugs. For this I was charged around £220 and when I got the car back I found the mechanic had wrecked a new K&N sticker which was on my air filter box. This is obviously a minor thing but to me it shows a lack of respect for my car.
Later I also found that when replacing the spark plug they had stripped the threads on one of the coil pack retaining bolt holes. To fix this the "mechanic" had filled the hole with silicone and then put the bolt in. Bodge job if ever I've seen one and I have never gone back because of it.
If I can't do the work on my 350 myself I now use a good local independent garage for smaller jobs, MOT's etc and take a drive to Horsham Developments (around an hour away) for anything more serious.
I know that when selling my car anyone who really knows anything about the 350 or 370 Zed for that matter will be more impressed with a good service history from Horsham Developments (the Cougar Store, Abbey Motorsport, TDi, RT Performance etc to name a few more) than any Nissan main dealer.