zkat wrote:

I'm trying to work out whether taking out a loan (3k-5k) to buy a car
a month or two ahead of applying for a mortgage is a bad idea.

Other things being equal, how will a lender treat an outstanding
(unsecured) loan? Will they reduce the loan amount? Will they ignore
it?

I think what they generally do is deduct (12 times) your monthly loan
repayments from your annual income before the income multiple is applied
to determine the maximum they will lend you.

If you want to maximise what they'll lend you, it would be a good idea
to postpone the car purchase until after your mortgage is approved.

Or buy an old banger intead.