If I had to divide up the UK into MTB regions then, with a bit of wild generalization to avoid a silly long list I’d go with:
Northern Scotland / Highlands: Where the wild haggis roam.
Tweed Valley: Cool kids camp
The Lakes/Cumbria, lovely if it would only stop raining for 5 minutes
North Wales/Snowdonia, see above.
South Wales Valleys BPW/Trail Centre scene
Peak District/Yorkshire region, basically the cult of Peaty.
‘Central’ England, really just Cannock Chase in the midst of sweet FA else.
Chilterns: Stockbrokers on carbon XC bikes.
East Anglia: Fenduro!
North Downs/Surrey Hills – Basically the Tweed Valley but with even newer T6’s
Southdowns: Spiritual home of mint sauce.
South West: Cider in sport