Off-road bike recommendations

[mattsccm]

Of those you listed any one would be fine apart from Muddy Fox which as now cheap and nasty, near BSOs, flogged from Mike Ashleys emporiums.
You need to decide : flat or dropped bars, suspension or not, ebike or not, single or multiple chainring or not. Do some reading, discard most of that and try a few out.
Scottish tracks that access lochs etc, if they are Land Rover width are often reasonably surfaced but equally I know of plent that are not.
All I would say is look at something with rack and mudgaurd mounts to cart you kit about on.