I think there are. Ours has got 130 members, there’s others ‘next door’ in all directions (centred around major conurbations) of similar size.
The function of them is quite different though – road clubs are centred around training and racing, and so post up results, wear club jerseys and are much more visible.
MTB clubs arrange rides, often on quite an ad-hoc basis for members through web forums, a few trips away, and the occasional event. Also ‘race jerseys’ don’t really fit (literally 😉 )so you wouldn’t know people are club members if you met them on the trail.
Around here there’s Newforce, Dorset Rough Riders, Berks on Bikes, SPAM, QECP Trail Collective etc