Not to many of these around anymore! During the 1980's Muddy Fox was the leading brand of Mountain/BMX Bikes, in the UK.
This is an early, rebuilt version of what they were designing. It comes with a fancy set of 26" Alloy rims, on a Hi-Stop coaster brake rear hub, and sealed Marin, front hub. Has been outfitted with almost all new parts, as you can see from the before (last) and after (first) photos.
I know that all vintage Muddy Fox bikes have a Cult following, and in building this I supplied fancy components, an excellent saddle, and a lot of time in labor.