Based on the bikes I’ve ridden round the Peak (Cove Stiffee, Giant VT, Santa Cruz Heckler, Ragley MmmBop, Cove G-Spot and Cotic Hemlock – crikey, that’s quite a lot!) the ones I have by far the most fun on (and, coincidentally, still own) are the Ragley and the Cotic.
So – something reasonably light that’s not too horrendous up the climbs, and that’s “sprightly” enough that you can get properly involved on the downs (so not the G-Spot!) but sturdy enough (I have Lyriks and fat tyres on the Cotic, Pikes on the Ragley) and with solid componentry that won’t get ground away after a few miles of grit.
I’ve no plans to change my bikes at the moment, but if I were buying new it’d be a Cotic Soul and Rocket.