I live here, as above, the official tracks are just that, gravel tracks that aren’t challenging, the bike shop in Burley has the crap maps or plenty to use via Strava. That said you can build some nice loops and it’s looking good at the moment with the autumnal colours. There are certainly places you can get more challenging rides near Burley ahem, it is getting much wetter though, but as 40mpg says might be best to contact Dorset Rough Riders or Newforce for local knowledge, and etiquette. Still bonkers there’s many miles of trails horses and walkers can go but not bikes, won’t go off on that one now.