I don't think you're legally bound. After all it says that if all the conditions (including financial ones) are not met you cannot take up the place, so i guess if you don't have the funding they simply won't send you the contract and you'll lose your place. I have the same problem, as I'm going to apply for funding in the next month or so but I'll accept the offer for now.
Also, I have to reply to my departmental offer, not the college one, and it's the college who sets the financial conditions... I guess you can't be bound to pay anything if you accept the department's offer.