A few answers for you:

Nope no GBS swab - well I haven't had it at least, nor has it been mentioned at all. They do make you do the gestational diabetes test though, even if you are low risk.

With regard to interventions etc, the birth centre does have "rules" that it has to follow which means you could end up in the birth suite (where the non-birth centre people give birth). For intance, if there is meconium in your waters then you have to get transfered so they can do continuous monitoring. Your midwifes come with you though and still provide the primary care, but they get advice from the OB (random OB you've never met before). So I guess that could be seen as a "potential" down side. (We were transferred due to meconium and the OB was quite nice - though at that point I didn't really care!). Oh and I should say that "transferred" means just down the corridor - only 20m!

The early discharge (if no complications) and home visits are awesome. We ended up with daily visits for the first 2 weeks - fantastic support. I would count down the hours till our MW came and I would write a list of questions for them - though I guess as a second time mum it probably wouldn't be as important.

It is not an easy to decision to make, but I think that you would be paying an awful lot for an OB, and I'd rather spend that on a holiday! But it is such a personal choice.