Hi Richard,
I used them to service mine for the last few years I had it. Some mixed feelings about them, but nothing to put me off.
They are very basic, and tend to be busy. That did mean sometimes an MOT and service ended up with the car in for a week, as they'd look at it, order parts, then start something else and seem to forget me. Not an issue, just need to keep on at them.
They know 944s inside out, but also tend to have young lads working there so need to be supervising them properly. This was where RPM fell down so badly, and ended up doing significant damage to my car, but I guess that's the problem with all garages.
They were always pretty competitive with pricing, and honest about what needed immediate attention, what could wait a year, and what should be done based on my budget and expectations. Nice that they took my mileage and driving style in to account when recommending work.
But, they did mess up at the last service I had before moving down here. I needed some welding for the MOT, and they told me it was a major job needing about 10 hours labour, but they didn't want to tackle it as it wasn't their speciality. This led to the car being laid up for a year, but when it went in to a specialist welder it turned out to be a £50 job, done in an evening. I wonder if they were just trying to get me to take it elsewhere for the welding and over-emphasised the work needed, but it didn't sit well with me.
Personally, I was going to try Ninex at Maidenhead for the next service had I not moved. No experience with them, but I was minded to try an alternative as I was in two minds about Chelsea Carrera's interest in the 944, with them being so busy with 911s and newer models such as Boxsters and Cayennes.
Hope that helps, probably not!