Hot Pogs are brilliant.
https://www.hotpog.co.uk Worth waiting for them to be in stock.
Made out of similar material to carradice saddlebags.
Most of the Canadian/USA ones are neoprene - that makes hands sweaty and then they freeze - avoid.
Made in Nottingham.
Plenty of room for hands, extra mitts if needed, gear and brake levers, flapjack, growing banannas...
Importantly, they keep your fingers together for mutual warmth, not in individual tubes like gloves.
I've used them for 5-6 hour rides in proper winter weather. Mine are the £60 version
The price is nothing compared with the money I have wasted on "winter" gloves.
Only for flat bar bikes. I tried another brand that were supposed to be OK for drops, but they made the bike uncontrollable because they are vertical and catch the wind. Really dangerous.
Trust me, I know about cold - we had no electric for 6 nights and days. Neighbours still not back on power.
No investment in the infrastructure