I delivered at the Royal Free last year.
Positives:
Easy to get to, same parking zone for us and I had most of my anti natal appointments with the same community midwife at my gps surgery. Very convenient. This same midwife also visited me several times during the post natal period which was nice.
Birth centre and labour ward are on opposite side of the same corridor. I was in the birth centre but did have some interventions, they came to me, I didn't have to move anywhere.
Negatives (for me):
Only one birth pool. I knew this but wasn't sure how much it mattered. For me, in the end it mattered a lot. I really wanted to be in the pool, unfortunately someone else was using it. I really feel this made a big difference. I did the tour at the RF, their line on the one pool thing was that they have big baths in every room anyway. But the baths there weren't deep enough to submerge me in warm water (to keep me warm) in the position I wanted to be in. Also they don't let you deliver in the bathroom.
UCLH I didn't choose it because it is difficult to get to and is so so busy. People have said to me since I might have got a better outcome there. I'm skeptical though, I had a long birth with some interventions at the end, I think this is more to do with bad luck (birth pool busy, midwife I didn't click with) and NHS protocols (eg once you've been pushing a certain time they want to intervene), and my choice (E.g I accepted the intervention of the induction drip, late in my labour which probably made things worse not better). A friend at UCH was encouraged in a similar situation to have similar interventions, she declined them and got the natural birth she wanted, but due to having a v experience doula friend advising her over the phone, not due to hospital differences.
Possibly if a pool had been free at UCH things might have gone better.
I wish I'd looked at the Whittington, has much improved recently with a revamped birth centre, birth pool in (nearly) every room. Offers as standards things I was hoping for like a natural third stage.
For me, what would have made a difference is a guaranteed birth pool and a midwife that already knew and understood me. But you don't get either if those on the NHS in London, anywhere!