DS1 started at The Hospital Day Nursery back in 2004, and then DS2 joined him there in 2007 - he left there a year ago, so I don't know so much about it now. It was set up by a former nursery nurse who was lovely - really friendly and great with the kids. Since then, they've opened a second nursery (Jumping Jacks) so some of the staff moved around. The hospital site is in a dedicated building which was new in 2004 and built specifically to be the nursery. They've got four rooms - broadly 0-18months, 18mo - 2.5, 2.5 - 3.5 and then 3.5 - leavers. My experience was that the latter rooms were particularly good - lots of activities and free access to the outdoor space as well. The nursery is set up to serve the hospital, so there are some spaces reserved for hospital staff (and a discount) so if you're non-NHS you have a slightly smaller allocation of spaces to bid for.
The nursery is open longer hours than most to accommodate hospital shifts, which can be very handy, and the prices were certainly competitive when I first looked into it. (To be honest I have no idea how prices compared after that, as once we were in I never looked elsewhere).
I did get some negative feedback from a former member of staff that suggested staff were not particularly happy with the way they were treated, but I don't know if that was just that particular (ex) staff member. She did say, however, that the kids were very well looked after, and it was just the staff that felt less well treated.
Overall I was pleased with the care given to my children while they were at the nursery, and found many of the staff were very loving and caring towards the kids.