Lewaney how early are you planning to go on maternity leave? I moved house while pregnant with DS so had to switch midwife teams and hospitals, it was fine but took a little time for the transition as they essentially had to re-do my booking in for the new hospital so repeat blood tests, midwife booking in etc. I was only 24 weeks at the time though so that wasn't a problem just had to wait a few weeks for the appointments. I don't really know why as you'd think they could just pass on the records from the old hospital, but it didn't work that way for some reason.
If you don't go on mat leave until 36+ weeks then it might be a bit stressful, you could go into labour early for example and London hospitals are usually super busy so I would expect more delays trying to book in to one of them (I moved out of London so was easier!). I'm sure it's possible though, just an added stress I wouldn't be keen on at that stage. Travelling to London for your appointments might be less stressful overall if everything is straightforward, but you still have the issue of if you need an emergency appointment, extras scan, monitoring etc while you're still in Bham then you wouldn't be registered locally and wouldn't have a local midwife to call if you have concerns although you could always go to A&E / EPU or similar to be seen. Personally I would probably book in to a local hospital in Bham and then you can always reassess when you get closer to your mat leave and switch if you feel comfortable with it at that stage.
itsnot sorry to hear you had such a rough day yesterday. Pregnancy can be extremely tough even without everything else going on, I'm sure you're not overly snappy but even if you were that's a perfectly natural response to constantly feeling like crap and people who can't be sympathetic to that should stay away! We're growing whole new humans here, it's ok to find it difficult, draining, emotional and overwhelming at times because it is all those things and sometimes you don't have energy left for anything else so the best thing is just to go to bed and hide for a while until you feel better!
My DH is great at practical support but terrible at emotional support, he just thinks I am making it all up should get on with things and distract myself and then I'll be fine. That or I should go to the doctor because there's clearly something wrong with me as it shouldn't be so hard 
Last time he was working away for most of my first trimester so he didn't really see this bit and I am worse this time, but still you'd think he could try to be a bit sympathetic, give me a hug after I've just thrown up again and ask if I'm ok instead of ignoring it completely for example. Seems so simple to me I don't see why he can't get it. Sorry, bit of a rant! He's away for most of this week and although it's hard work juggling work and DS on my own I'm sort of enjoying it because I don't have to pretend to be ok all the time and I get the bed all to myself!
miss that doctor sounds incredibly mean, may be overworked or had a stressful day but that's no reason to take it out on you. Hope you get a nicer one today!
I have mixed feelings about Facebook announcements, did one last time out of laziness really (too many people in far flung corners of the world to text/write to them all) but probably won't formally announce this time, just tell people as we see them. We were trying for quite a long time with this one and I did feel a twinge of sadness at pregnancy announcements sometimes, but always more happy for the couple and would never have thought they shouldn't publicise it. I can see it would be harder for those who have suffered mc or facing more serious fertility problems though. However I have just seen a good one on my fb where they had the scan pic on a Christmas bauble hanging on their tree (no idea how they got it on a bauble?), with another hand-painted bauble showing the due date.