I think there are loads of things to consider, Bella. But the main thing for me was to be happy with the way the carers speak to the children. At our centre I am very happy that the primary aim of the creche teachers (where P is) is to provide as 'homey' an environment to the kids as they can. Lots of cuddles and kisses etc. I looked at a few places and our current centre was the only place where the director spoke to Natalie, not just me when we visited. It sounds like a given, but at our centre they all seem to really like kids and I think you can find places where that's not the case.
I would totally recommend having a look at several places. I was happy with one place until I looked at our current one. Then the other one looked much less good. LOL! If that makes any sense! I also like the newer facilities, the play area has an 'older kid' section and a younger kid one, the toys are in really good nick and the artwork the kids do is proudly displayed. I don't care about the academic stuff they do, although I know they do it - they follow a govt syllabus, but that's not as important to me as their interaction between carers and kids.
HTH & GL!!