I looked into this in some detail, Angeliz, as dd2 was still breech at 37 weeks.
A big study was done a few years ago which showed that statistically there was a slightly increased risk of 'soft' neurological problems (that's things like adhd) with vaginal breech births rather than caesareans, and this is what Doctors will quote to you. BUT if you look at this study more closely, it averages out enormous differences between women across a huge range of countries, birth environments and birth methods, so it doesn't really tell you much to help inform your own decision.
The main problem in the UK is that because so many people go straight to caesarean with a breech, that midwives and doctors have become 'de-skilled' at assisting natural breech births (and this is what the consultant actually said to me). So there is a vicious circle, in that problems can arise from the inexperience of the practitioners rather than from the birth position itself. For example, I asked the midwife how many vaginal breech deliveries she'd done, and she said hadn't seen ANY in her 4 years at the (major London teaching) hospital.
The upshot of my deliberations was that if the baby had stayed breech, I probably would have tried for a natural birth (I'd had uncomplicated births with my two older ones, who were both 9lb+), BUT I would have wanted to be accompanied into hospital by an independent midwife with experience of doing breech deliveries.
I found \link{http://www.aims.org.uk/Journal/Vol10No3/handOffbreech.htm\this article} very useful, by the woman who seems to be the UK's doyenne of vaginal breech births, and her view is that breeches should not be induced or augmented, which seems sensible given what can happen in any birth once they add in syntocinon etc. Although I really wanted to avoid a caesarean, I would still prefer that to the legs-in-stirrups, forceps and epesiotomy-up-to-the-navel scenario, which I suspect is what would happen in a standard uk-delivery suite once the doctors got involved.
In the end I had an ECV (external cephalic version) which is a manual turning of the baby, and successfully turned dd2. It's not done till 37 weeks, though. Ignore any horror stories you hear about it -- if done by an experienced team it's pretty safe, not agony, and successful with more than 50% of 2nd time+ mothers.
hth