Well, that appointment was largely a waste of time, much as predicted... 
In fact if it hadn't been for the GBS result (today's urine sample clear, BTW) there'd have been nothing at all to talk about, and a medical student wandered off with my notes so in spite of having a 9.10 appointment I had to sit there for ages and ages and ages waiting to be called.
GBS discussion was generally as positive as I'd have realistically hoped for. Hospital policy is that I am now deemed to be GBS+ and should have IV antibiotics during labour have big luminous stickers on my maternity notes to that effect and everything and that therefore because my labour was quick last time I should come in as soon as I get twinges so they can get me on an IV. But if I don't get antibiotics 4 hours before the baby arrives they won't automatically put the baby on IV antibiotics but will get a paediatrician to assess and decide whether it seems like a good idea or not. She was generally in favour of my getting a private ECM screen done at 35-37 weeks, though (it wouldn't change their policy on whether they wanted to put me on IV antibiotics but would factor into paediatrician's assessment).
So what I'm actually going to do is get the 35-37 week screen, then if that comes back positive do as per policy and go in at the first twinge. If it comes back negative I'm going to assume I don't have active GBS (which is what all the studies would support), stay at home as long as possible when labour starts and probably not have the IV antibiotics (last time I got to hospital already in transition, and I don't think anyone will be able to get near me with a needle when I'm in transition...).
So, we have a plan. Well, they have a plan and I have a plan and they overlap in at least some details
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"20 week" scan booked for 19 October (21+3), and next proper appointment at the Diaban clinic on 9 November to be issued with my little clicky blood test thing on the assumption I'll have GD this time round as well. So a couple of months of twiddling my thumbs in the meantime...