Looks like it has been one of those days, weeks months, years etc.. 
What a blow OneMoreOne. I do hope that the rest of the chain are understanding & that the land registry don't take too long to get this sorted for you. 
We have a similar situation Artus, except ours isn't a newbuild we're hoping to buy. The vendors agent has given us a date of 27th February before they will be looking into remarketing.
Hopefully things come good for us both by then. 
Welcome bigsighall. Great & appropriate username!
Any idea what the hold up is? 
Welcome back timeforheroes. So glad to hear that everything has finally come good for you after such a nightmarish journey to get here. Hope the move goes to plan today. Do pop back & keep us posted? 
Fingers crossed Highheels 
Im so sorry Mussinboots.
What a shitty buyer you have.
Its so hard to know what to suggest, because only you know your circumstances & what you need to do, or if you can even afford an extra 10k at the moment! If it were me id probably call her bluff & say, no can do. Not a penny more in the pot, take it or leave it. Chances are she won't, but you never know. Is there any truth in what she is saying about prices increasing so much in a few months? I find it hard to believe tbh! Big ((Hugs)) 
We had a shitty day yesterday too. Got some really offensive feedback from some timewasters who viewed. Its hard not to take it to heart, but ive woken up today debating whether to ask them to explain it or not. Have messaged our EA to see what she's got to say. All other feedback has been positive!