I'm a bit surprised by the bad stories you've heard, it's unfortunate as I and the majority of my friends (at least 4 or 5 in the last 2 years) all gave birth at UCH with fantastic experiences. So at least from our end, all good!
I gave birth nearly a year ago in the birth centre. They were very much leaning on the side of anti-intervention, from antenatal through to the labour itself. If you opt for the birth centre they encourage you to go for as much as you can without G&A, then to wait a bit before the pool, avoid the use of drugs etc. They really want to avoid epidural as that means a transfer to the labour ward. They have a lot of equipment and I found they were keen to stick to my plan as much as possible whilst offering helpful ideas to keep things going. They have much more staff in the birth centre than is available on the labour ward, so they encouraged women whilst antenatal to opt for the birth centre whilst I was there.
In terms of my birth, they held out as long as possible. I was in the pool room, I used G&A from around 4cm (I needed it! Never got around to the pool because labour progressed faster than originally expected - about 6 hours from 3cm to 10cm) but I was pretty much left to get on with things in the way I felt comfortable with, they helped me with breathing, offered different tips and equipment (eg birthing ball, positions to be in). When it was time to push things slowed down, so they helped me with different positions on my knees and then suggested the birthing stool. I pushed for 2 hours but it was actually alright, not horribly painful (!), contractions had moved to 5mins apart hence the time it took plus DS has quite a big head and struggled to move over the 'bump' in the birth canal (no idea what that's actually called).
They said that once you get to 2 hours of pushing they have to seriously consider intervention, to avoid complications/distress, they were worried about needing to intervene in our case but they really encouraged me with pushing and breathing and just before 2 hours DS suddenly came shooting out (only way I can describe it!). They immediately had me reclined, G&A, breathing techniques to slow down and limit tearing. Baby delivered onto stomach and they focused on getting us both well and happy, I had torn and he was a little pale. Frankly they were brilliant. I had 2nd degree perineal tear which was expertly stitched, just a bit swollen after, plus an 'unusual' (according to MW) vaginal tear, also well-stitched but had some problems after due to me overexerting
but it still healed up and fine within 1-2 weeks.
It was only the other day that DH told me that I was very close to requiring serious intervention, eg EMCS
I remember them regularly looking at the clock and saying, "Let's give it 10mins more, come on delasi, I want you to take a deep breath, really bare down..." etc, so I think they really did their best to avoid intervention and it worked.
I would definitely go back for future DC if I can.