Just found a diameter calculator on line, the 235 are 31.73 and 275 are 31.65, so pretty much the same.
Getting back to the original questioon, I e mailed via the contact us button on their website about the Marix Lions, not a peep back after a week, don't think I'll be going there.
Who are Insa Turbo stockists in Scotland, or is mail order the only option?