Good luck tomorrow squiz Try to focus on the fact that you are going to see your baby again! It's been a while since the last scan, hasn't it! It will have changed sooo much 
Welcome to all the newbies I do recognise some names from the ttc threads. So glad that you are able to join us.
London Poor you, please try not to worry too much. All chances are that this is not even pregnancy-related. Or, as squiz says, if it is, it will be easily treatable. Could you be low in iron? This causes breathlessness. Plus, your body is producing a lot more fluids all over, which have to be stored somewhere, so air passages/lungs etc can get a bit squashed. Your baby is getting everything it needs, they are very good with that.
I have decided not to have the CVS tomorrow, I'm opting for amniocentesis instead. At this point, for me, the slightly lower mc risk outweighs the longer wait for the procedure and results. I have waited so much and so long by now, another 2 weeks does not make any difference.
Now trying to decide where to have it... My local hospital (very good reputation, big maternity unit, very good equipment etc.) can fit me in on Monday, the FMC in London only does the procedure on Wednesday (if the Prof is to do it). Much of a muchness date-wise, results take 3 days to come back for both.
Uhming and ahing of where to go - I have been getting excellent care at my hospital and feel very well looked after there, whereas my personal experience at the FMC has been a bit 'meh' overall - not in terms of the medical care, but more the emotional side of things.
But the Prof at the FMC is meant to be the best... On the other hand, amnio is a very standard procedure these days... Plus, I wouldn't have to go all the way to London and back... But do I not owe it to myself, DH and baby to get the best possible consultant?
Decisions, decisions... Doesn't help that I am completely snowed under at work at the moment, I have barely the time to get all my tasks done, let alone make life-changing decisions.