Bloss- you need to keep this bumped. Have you checked out what would happen if you went down the emergency route. I'm not 100% sure but I think that if you self refer to our local out of hours service, you will get seen by the on call NHS dentist. That could be a cheaper way of doing it. Alternatively where's your nearest dental school? Could you get cheaper treatment there?
I think it would be worth ringing your local NHS trust and making enquiries.. Have you got any health care cover in place? I know ours only covered us for emergency dental treatment of £200 in aus, but it might be worth trying.
If you get no joy, ring me or email me, you've got the numbers and I have a friend who works for a private dentist in the village as his office manager. She could give you an estimated price to compare with your quote. If it's way cheaper you can come and stay and have it done here!
In the meantime, thinking of you.