I had a lovely long chat with the Fuji rep at the open day. She was of the opinion that as long as I got UHS II cards at V60 or more, then they should be fine. The list from Fuji are just recommendations, not compulsory. If I want to do high speed video, then I should use V90 or CF-Express cards.
So, I have ordered some of these
https://www.amazon.co.uk/gp/product/B074M64L1L and will test them out when they arrive.
Alan