UCH is very good (I've had three there, spread over nine years).
The actual building is a bit (!) rundown, as they're in the process of building a shiny new hospital on a next-door site, but the actual care is very good IME, and that of all my friends. Unlike Hester, I don't know anyone who's had a bad word to say about it.
They have a new low-tech birthing unit in addition to the labour ward which is well worth checking out, as it seems to be run slightly separately to the main delivery unit and offers midwife-led natural births. Overall their stats for interventions are probably above average as they take all the complicated cases from elsewhere, including the Portland. The consultant that I had is Mr. Silverstone, who is really lovely.
The Foetal medicine dept. is very brilliant (Mr Jauniaux) as is the neonatal unit (each of my three was there for observation).
Yes, the building is grotty, and yes, they suffer from the usual inner-London midwife shortage, but overall, very happy.
CAT doesn't work for me, but if you want more details post here and I'll send you my email address.