Thanks for the comments.
Some answers:
9mmQR but my Hope hub will convert according to the LBS.
I most often ride cross country in the Cotswolds since that’s where I live but I go to Cannock when I can and have been over to the Marin and Penmachno in Wales a few times.
Shortlist based on current offers I’ve found online looks like this now:
RockShox Sektor RL Solo Air 2014 £265.99 Winstanley
Rockshox Revelation RL Forks 2013 £278.96 Merlin
Rockshox Sektor RL Dual Position Forks – 26″ – 2014 £242.96 Merlin
RockShox Reba RL Solo Air Forks – Pushloc 2013 £251.99 CRC
Revelation RLT Dual Postion Air Forks 2013 £292.50 merlin
Rockshox Revelation RLT Forks 2013 £315.00 Merlin
Fox 32 Float 130 RLC Fit 15Qr £314.99 JeJames
Fox 32 TALAS 140 RLC 2009 £314.99 JeJames