Buy a cheaper car - have lots of savings left :)

Why not put a proportion of cash to the car purchase, and find the remainder through a personal loan. You can use comparison sites to get a loan with a low APR. This way the finance isn't tied to the car. Obviously only you can decide on the proportion you can afford to fund through the personal loan, and the proportion you can pay in cash.

You could increase your mortgage, but that would require an arrangement fee, could be £500 say, plus the interest. You could take out a personal load with your bank, you often get good terms if you are a long term customer. Some credit cards do 6 months with no charge deals, which could be worth using, just make sure you pay before the free period lapses, or you'll be stuffed. Or if you have some investments, you might want to realise them.

I recently was in a similar predicament. I contacted Nationwide about a personal loan, but it was so complex I gave up. I decided to live on the edge, using cash to pay the bill, and sell stock market investments if need be. I worked out that the loss in future growth from selling investments would be no more than the charge from Nationwide for a loan, and probably much less. With luck I will not need to sell any, but they are their in case the wolf arrives at the door.