I had a baby at UCH in 2013, and can vouch for the clinical care being excellent. You're assigned to a named midwife team so see someone from the same group of not the same person. The scanning team are excellent, and you have the combined test results back within an hour of your 12 week scan, so no worrying for days about that.
But, I ended up with an emcs for foetal distress, and would say the post natal ward is pretty dire.
I was in labour for 36 hours prior to the emcs, and I was exhausted, emotional, and found it overwhelming. It was noisy, crowded... We asked for a private room, which we had to pay something like £180 a night for, and that made it bearable, (other than the cost!). I was in tears through exhaustion at that point so we didn't have a lot of choice really. There was no prioritising of those rooms by clinical need, by the way, just willingness to pay and first to ask.
I'm now 13 weeks pregnant again, and back at UCH, as I found the antenatal care so good. It's sill good. I'm thinking of swapping to the Whittington for the birth, but am undecided. I will probably have an ELCS this time around, so I will need to stay in at least 2 nights and I hate the thought of 2 nights on that busy ward when you really need sleep!
As a pp said though, post natal care is bad across London... So it may not be worth changing.