The other reason they don't usually do an ECV before 37 weeks is because, infrequently, the procedure can cause distress to the baby such that it needs to be delivered by CS - and they want to avoid doing that to a pre-term baby. It is RARE for this to happen, but it can happen.
Having been in the 3-4% of women who's babies remain breech, I personally don't think its good advice not to discuss this till 37 weeks. I can see that if you're in the majority where the baby turns then you've been saved unnecessary worry. But if you're in the minority, stubornly breech group then it can all come out of nowhere.
My experience with the NHS side was that, once I'd been scanned as breech at 36 weeks (I was able to push for an earlier scan as CMW was palpating "early" ) I was booked straight in to see the consultant. At that meeting, I was basically given the choice of a successful ECV or a CS. When I asked outright, they said I would be "allowed" a vaginal breech delivery - which would be obstetrician led, in theatre ("just in case"), in lithotomy, with forceps (and so quite possibly an episiotomy) and with a large supporting cast ("it sounds like a lot of people, but some of them are just there for education because breech births are so rare" - nice to know they were going to ask my consent, then!). Justification for recommending a CS was the Term Breech Trial - "we know its flawed but it's the best we've got." They wanted me to make appointments for the ECV and to see the anaethetist then and there - if I had been 37 weeks+ there would be very little time to go away and think about it as they'd want to schedule the CS for 39 weeks. Plus the fact that the way the Obs presented the information there really wasn't that much to think about - does that version of vaginal birth sound tempting to you?
Fortunately I'd already had a chance to do some digging of my own and talk to experienced midwives. I knew that the Term Breech Trial wasn't worth the paper its printed on, and it has been thoroughly discredited on both sides of the pond. I strongly felt that the information given to me in that meeting was more than a little skewed towards keeping me in their comfort zone.
By finding out early, I was able to take the time to do my own reading and make my own decision. For me, that meant talking to IMs and, very fortunately, finding some that had the capacity to take me on at that late stage. One of the other reasons we went with IMs was that we were disilusioned with our NHS CMW by that stage (ignoring the whole breech issue we wanted a homebirth and she wasn't particularly supportive) - there are still breech midwifery skills within the NHS and a passing comment made by one of the midwives at the hospital did make me think that a hands-off, midwife led breech birth might have been possible with them. If I'd wanted to follow this up I'd have been talking to the Head of Midwifery and doing my best to sideline the consultant. Sadly these skills are reducing within the NHS (as so many babies are born by CS), so that might have turned out to be an impossible dream.
Sorry - this has turned into a complete essay and a bit of a brain dump . I just think that the way the NHS handles breech babies by default isn't necessarily in the best interests of either mothers or babies. I felt very much like I was chucked into what some statistician with poor data had decided was the best course of action, without anyone bothering to find out whether it was appropriate for me (what on earth was I thinking, expecting individualised care ?)
I wish I'd been pushed to be a bit more pro-active when I was palpated as breech at 28 weeks, 32 weeks, etc, as going through the NHS breech route at 37 weeks when there isn't much time left for your baby to turn is far more stressful than if you start early when anything you do is more likely to work. And now I'll shutup. finally. (sorry )