Who has been through Mortgage Market Regulations questions and stress testing and can tell me about it?

[TheBadTemperedLadybird]

Ideally with Santander. Is there anything we can do to make sure we pass? We have debts but all on 0%, high income, good LTV. We want to change to interest only so we've been told we'll have to go through a full MMR even though it's our existing lender. Thanks. We use our authorised overdraft, do we need to get rid of this first?

Your debts being on 0% is irrelevant. Having the debts in the first place is not a good place to start. Do you have any unauthorised overdraft usage or bank charges? Have you made any late payments or missed any in the last six years? What are your reasons for going onto interest only? What is your repayment vehicle? Do you have children? If so, any childcare costs? What is your income? What is your balance and LTV?
I know that is a lot of questions but there is a lot to go through.

Disagree about the debt - 0% borrowing that you can afford to pay off is a perfectly sensible way to finance something. They didn't care about the debt as our income is v high. Ltv is 20%. Credit rating is excellent
Anyway we passed so that's ok. No childcare costs.

We applied for a mortgage with Santander this summer, borrowing 60% of purchase price. No debts, reasonable income (applied to borrow about 4 x joint income), but we did have high commuting costs and childcare costs to factor in, which came to about a quarter of our take-home pay. Our mortgage payment was another quarter.

We had no problems and were approved very quickly once they had all the relevant information. It may have helped that we both have current accounts with them so they would have been able to verify our spending habits quite quickly.

We were also approved for the full amount we wanted to borrow, which wasn't far off the max they were prepared to lend us.

They stress tested us to 12% though, asking whether we could afford it at that.