Greyville are the distributors and they recommend Dotbike as the best source. I contacted Neil at Dotbike and he got the latest shipment today, however all 24 of the 26" version have gone straight back out on pre-order. Luckily for me I wanted the 700x35 version and he had 3 in stock following todays delivery so I've just ordered a pair. Humerously they're actually lighter than my existing 700x35 M+ tyres

so I shouldn't see as big a performance drop as someone going from 23mm slicks might.
What I'm hoping for based on reading up on them - fit and forget from start to end of Winter, should get 2-3 Winters out of a pair. A 1-2mph drop in average speed in non icy conditions. Peace of mind that, whatever the temperature does through Winter I can still ride.
I hate the thought of being forced into not riding and can't justify the risk of keeping speed higher against the cost of a pair of tyres and a couple of mph. I'll rport back on how I find them.