I live in Macc and would recommend it. Not just for the MTB but it’s definitely a 15 minute town which somewhere like Leeds or Sheffield certainly aren’t, everything you need is pretty much walking or a short bike ride away. We have nice pubs now (we didn’t when I first came here 28 years ago).
I used to go to London once a month with work and the London end of the commute to Borough was much worse than the journey down to London. However trains are far worse these days you could easily end up paying £400 to sit on the floor by the nonfunctional toilet and rammed train but that’s the same everywhere.
We have good mountain biking as stated also gravel and the road riding is great as you can go into the hills or ride for miles on the Cheshire plain. Also it’s a short train ride to Manchester for some culture I was there twice a week for gigs before Christmas packed in Ideles, Fontains, Prodigy, Nick Cave amongst others. We also go to Buxton, Stoke or Crewe a lot to the theatres especially for Comedy.
Its also full of Scottish folk, including my mrs, though that might influence you either way.