Yeah even that is a stretch.
I think the people are just trying it on with you man, in England a wolf is not a common fish, and thus these people are probably not total beginners, and hence - they probably know £90 is way over the market value of a 1 foot mal.
Finding one at a foot is probably not that easy, certainly when they are imported they're more likely to be half that size, and foot longers are usually going to come from private sellers. So the chances of you finding 1 or more foot long mals in the very near future are slim, so if you really want these fish just haggle.
I've done it plenty of times. Simply say that's over the market value of these fish, who else is gonna buy them at that price?
I had trouble selling my 10 inch mal. They are cool fish, but not many people want an inactive fish that should really be kept alone.