Craig, don't you check over customer cars for damage when you receive them and before you hand them back? 
Gone - Range Rover Supercharged 2006

Update:

Ended up speaking to the service manager who said they take these issues very seriously. The dent wasn't marked on the job sheet as existing when it went in (in fairness, you have to be tall to look down on the roof). He has interviewed the technician and the Valet company they use, neither had any knowledge of the dent.

I asked about CCTV, but was told that it doesn't cover workshops or washing area.

He did offer to get his "dentman" to try and sort it and said they would put pressure on him to do it at a lower price given that RR dealer gives him a lot of work. They offered to do it at their premises and in case it needed the roof lining or sunroof taking out, as a goodwilll gesture, offered to do this at their cost.

All in all, thats probably the best I could expect - I cannot prove it happened there and in reality, I wouldn't want anyone to get fired for it (even though I am still 99% sure it wasn't dented when I dropped it off).

So at this point I have to say experience at dealer 50/50 at best, however, they have responded well to the problem in the circumstances.

Goes in next week.

But does the CCTV cover the points where the vehicle arrives and where it leaves the building? If it arrives without a dent and leaves with one then they're liable. Doesn't matter who did it while it was there. I'd expect the cameras to be high enough to see the roof, but whether they're good enough quality to spot the dent is another matter.

Final update:

Car went in yesterday and their dentman got most of it out - its still there, but you have to look for it.

Now the bad bits - the Plastic strip that runs along the roof was badly refitted, when I looked at it, 2 of the clips that hold it in had been broken (the broken tabs were still in the channel).

Secondly the rear wash jets had been changed at the time of the service (£90) the wash only worked for a day then stopped again, so I asked them to relook at that whilst it was there - they did and surprise surprise the one-way valve was now faulty - so they changed that & it works. But, they have obviously fitted the wiper arm back in the wrong place on the spline, so instead of been hidden at the top, it is part way down the rear screen.

Both small things, I will sort them myself, but to be honest I think its really shoddy not to do these things properly.

I went to the main dealer to keep up my service history and with the car being new to me, though it would be good to get the car checked over - my experience with these guys has shown that all they want to do is standard service's on cars under warranty. So thats it for me, I am going to find a quality specialist.