Sheffield – not bad, but there is only really the Dark Peak within spitting ditance, which is cool, but you could cover 95% of it in 4 rides (stanage loop, hope/edale loop, cut gate, jacobs ladder).
I’m going for the Peaks side of Manchester, almost as close as Sheffield, but 90min drive from the Lakes and a lot of Wales as well. And there’re enough jobs to make it viable for just about anyone, which would be my reason for not going to Sheffield (or a lot of Scotland). Scottish borders would be cool for biking, but rubbish for jobs, or being close to fmily/friends, I’d usualy put MTB in the ‘must not be crap’ list of criteria rather than a must have.