Ole, the professional hardware stores here (industri och bygghandel) have imperial nuts and bolts, as well as dies and taps if you want to make your own inserts or drill-out and rethread a metric one. They don't carry things like t-nuts though. Another good local source would be a local branch of a UK car club: I sometimes used to get imperial threaded parts here from the local MG owners club.
I just had a quick look though my favourite suppliers in the UK (both amatuer DIY and lab suppliers like RS components) and you're right, they are all metric now.
McMaster Carr (www.mcmaster.com) will ship internationally and have several sorts of "Tee Nuts" in standard imperial threads.
Surely those Scottish rigs are built with imperial fittings. They won't miss a couple of nuts now will they....