Yep I was going to suggest you up the re-mortgage value a bit to cover the cost of a car, if you were already budgeting to repay a car loan anyway (say a couple of hundred a month for ~36 months?) still do that, but as overpayment on the mortgage. paying down a mortgage faster saves you interest over the longer term anyway, you’ll have the option to simply stop those overpayments if you need to reduce you’re outgoings at some point without defaulting on a car loan and losing your vehicle, and you’ll hardly notice the difference that extra £6k makes to the basic monthly mortgage repayments (depending on the life/value of the mortgage of course)…
Just talk to the broker and explain what you want to do, he/she is bound to have some advice…