Hi velocipede, I grew up in the Melton area, and TBH it depends what you mean by “good riding”!
Belvoir (its pronounced beaver) woods (and the whole belvoir estate is pretty good, but muddy, and really sticky clay mud at that! I used to ride up to the castle from Redmile, take a right on the track across the fields (possibly a footpath?) down to the bottom, up the hill again and then take a right, following the woods across to Stathern, but its all a bit open forest trail (at least it was 10 years ago). There is plenty of potential for cheeky singletrack in those woods and we built at least 3 sets of jumps/ DH runs over the years!
Up and down and around borough hill out the other side of melton is the only other specific place I can think of, but its not much. Most of the rides we did were XC jaunts, following various bridle paths and farm tracks just linking huge loops together.
Have a look for the viking challenge, it sets off from my old school in Redmile and is i tihnk 40 miles of MTB ride, should open your eyes to some new areas to explore.
It is roady heaven round there, with loads of quiet lanes, undulating roads and shelter from hedges, Sorry I can’t think of many more trails at the moment, I’ll have a dig through some maps and see if I can remember any other routes we used to do!
(Also trials at asfordby mine!)