When you say you'll take a massive hit, how much are we talking? As you didn't pay for the car outright, it won't be the difference between your invoice price and what you sell it for, it will be your deposit plus payments, minus any equity (or plus the negative equity if that is the case.) That's not the whole story tho', because since October, you would have had to have had a car of some description to drive around in, so that would have cost you money in depreciation and servicing.
If you are able to find an extra £3k deposit for the house, over 25 years that will mean you pay back £5,800ish less, so it might be as well to take the hit now to save more in the long run.
As Graham suggested, you could extend you finance and keep the car, but that would mean owing more money on both the house and the car and even longer before you have any decent equity in either.