Given you have been forewarned about the issue I would say that changes the situation.
At the end of the day it's not you money, however had you not known it had to be paid back you could have a reasonable argument to say that you didn't know and arrange a fair repayment period, say �50 a month.
For me it really depends on how quickly you intend to pay it back if you did spent it, could you pay it back next month, if so I'd personally use it now and then when chased for the money say you will pay on X date (which is all you would be legally required to do).
With regards to then intending to recover from the bank, they simply can't do that (not a legal issue, to withdraw funds they would need you signature on a DD form or standing order).