I live near Leicester and the first thing I would say is try to be 'billeted' out of the city, but on a train line.
There is good(ish) MTBing to be had, but you need to ride the naughty stuff early to avoid being chased by rangers (aka the fun police). You can string together a reasonable 60% offroad route of 20 miles in Charnwood Forest if you don't mind riding footpaths and outrunning rangers in landrovers (anyone local knows where I am talking about). I can do a 110m height gain climb pretty much out of my front door, where there's hills, there's thrills - you just have to avoid people who want to clamp down on any form of enjoyment at all.
I have to agree with the 'casual violence' quote, though. I often said to my uni mates when we went out in Newcastle that there were lots of scuffles in the Bigg Market, but that they were almost governed by some unwritten code, in Leicester, there would have been at least ten people involved.
I've been out on the lash in countless towns and cities in Britain, and the only place I've been that's more intimidating is Oldham. You know, that kind of 'there's something bubbling under the surface in this place and it's going to kick off' feeling you get.
On the plus sides, though - very, very good for a curry and all manner of indian food and the best rugby team in the country!