Turns out my Clubman 8 had Dyform rigging.
Took the forestay down to a rigger today to get a new one made because the swaged on lower screw was a bit bent and he says it's Dyform.
I thought the strands looked a bit flat on the outside but I thought that was from the hanks sliding up and down over a period but not so; they are like that from new.
Makes a bit of a mockery of me changing the uppers to Dyneema when a previous owner or the manufacturer has determined that even standard 7x19 wire has too much stretch.
Kind of explains however why packing up the shrouds and forestay was such a pain in the ass prompting me to go for dyneema in the first place as Dyform is considerably less flexible.
Interesting but I sprung for the extra cost in the new one anyway just in case I want to go back to using the old shrouds.