I agree that the raw figures don’t tell you much.
What will you have in savings after moving? Most people run their savings right down in order to move, but if you’ve still got a buffer in the bank, you can weather a crisis if it occurs. So, if you can put aside/not spend on moving house a sum of 6 mo this living expenses, then S probably doable.
Also, what else do you spend on? After basic bills, how much do you still need per month? Will the higher mortgage allow that spending to happen …and that spending needs to include some pension payments and some saving, especially if your buffer is small. The basic figure increase if £400 is fine if it’s affordable. For some £100 more won’t be affordable and for others an extra £2k will be. It depends on your income and other expenditure.
Mortgages are there at least for the medium term so you need to consider prospects too. If there’s a good chance of big pay rises, it makes taking a big jump in mortgage payments more sensible than if you’re never likely to see another pay rise again.
Within all this, factor in an increase in mortgage rates at some point.
For those who have got decent savings and at least some prospects and have the ability to control their spending and cut down a bit for a couple of years if needed, pushing themselves on mortgage borrowing is often a good thing and something they’re glad they did, especially if it means getting the forever house and avoiding having to move again in a few years, which is very expensive.
It’s not good to leave yourself unable to pay bills or unable to deal with a small crisis like a new boiler being needed….but beyond that, most professional people who have some some cope if boosting their incomes (promotion or one person returning to full time work from part time etc) can cope with a couple of years of relative hardship and it’s worth it, for the longer term benefits. Many people look back and laugh at the mortgage payment they thought was so much and so stretching, and within a few years say it’s very manageable. But lots have a couple or few years of limited holidays and new cars etc, and for most people that’s fine and liveable with.
If you’re still able to put some money into your pension and save a bit and have some kind of buffer, plus ideas for boosting income if not now but in the next five years, there’s little point holding off pushing yourself…because what will you do with that money not spent on the mortgage? You’ll either just boost savings more (there’s time for that later as long as you’ve got some now) or spend it on cars and holidays (and putting it into property is better…for your lifestyle and for future value)….so only don’t do it if you can’t afford it.