Let's go with Leeds as it's a place I'm familiar with. There is a saturation of new build apartments from over the past 30 years. I've just taken a look and you could rent a 1 bed flat near the train station/city centre for as little as £800pcm or buy between £100 -150k and the monthly cost for that would depend on the interest on any mortgage you managed to secure. Obviously there are bigger and more expensive flats around!
We spend about £700 a month on food but I tend to buy locally which is a bit more expensive especially the greengrocer and butcher. However, we live in the north and have a fairly simple diet. Other towns may be more expensive.
Utilities are no longer cheap, you probably need to factor in a few hundred pounds a month, although a one bed flat shouldn't take much heating. We have a vast 1920s 4 bed home which absolutely guzzles the gas and electric despite having had the walls and ceiling insulated! You also have to pay water rates, I think ours is £130 pcm.
There is also the council tax which varies on the size and location of the property. You'd probably need to factor in at least £150 per month to cover that.
Our joint incomes (my workplace pension and part-time NHS job, and my partner's income) brings in around 40k and we have a comfortable life. However, we are into our 60s and already have all the stuff we need....in fact we moved 2 households into one so we have more than we need. If you need furniture etc you'll need more available cash!
There really is no exact science. As a single parent I brought up my son on a 45k salary back in the 90s/00s (probably close to 70k these days), but as I had not only a mortgage but creche fees to pay I was constantly struggling. Which is maybe why my standards are less exacting than others! Hope this garbled answer helps!