I live in London and have a number of hospitals roughly equally near me.
I'd like to have antenatal care at St Thomas's because it has a prematurity monitoring clinic which aims to avoid prem birth (my first DC was prem).
However I'd prefer to give birth at St George's as it's a bit closer and a lot more familiar to me and I think I'll feel more comfortable there.
Is this allowed? Are there disadvantages? Of course it means I wouldn't get the same midwives for birth as for antenatal but in my (limited) experience you never get an "allocated" midwife at these big London hospitals anyway.