I would agree with you Spantrout, usually a seller can back out of a contract on payment of double the deposit back to the buyer.
Another point to note is that we are all pretty much aware that a contract in Bulgaria is hardly worth the paper it is written on.
There is also the issue of how the contract was done and signed - if only written in English and not signed in front of a notary in Bulgaria - is it even valid? After all if money paid to a UK bank account is there any real claim in Bulgaria.
And even if there is a valid claim here in Bulgaria we all know how effective the court system is here! I very much doubt it will be as simple as going in front of a judge and asking him to authorise the transfer. I presume by writ Steven1404 means a notary appeal - basically a letter before action saying if x does not happen, we will go to court. Then its off to court and if mine and other people's experiences are anything to go by, a long and expensive procedure with no guarantee of any successful outcome at the end.