Now is the time to read the contract that you probably signed up to when BUNAC offered you the job. Have you got any grounds to cancel under the terms of the contract eg ill health?
If the terms of your having to pay a further £1000, if this is clearly set out in your contract and you signed it, unless the terms are legally unfair, you are probably on the hook for it. The fact that you are a student and finnancially challenged is unfortunately for you not BUNAC's problem. If you haven't signed a contract, you would be in a better position to refuse to pay.
You could try your Student Union for some assistance, they may have had students in this situation before.
Last edited by edjunkie; 10-05-2012 at 19:46.