Filson's reluctance to ship to the UK has nothing to do with Brexit. It predates Brexit and applies even when the goods are well over the £135 threshold such that there is no extra paperwork for them to fill in. Please quit the misplaced political moaning, this isn't the right forum.
A google search does not show anything by Filson called "Guide lodge pants", nor do I see anything by that name on their US website. Closest are lounge pants which are pyjamas. Do you have a link? Not that it will help solve your problem, but it would be good to know what you are looking at.
It has long been a hell of a job to get Filson items that were not on their European web site. I wanted some Mackinaw field pants back in around 2010 and had to have them shipped to a US address for me to collect when on holiday
Eight years later, by which time you would think they would have got with the idea of on-line international sales, someone I know wanted a Filson Mackinaw wool bib and we ended up having to have a pair shipped to a hotel in New York, picked up by someone travelling to the US, then they in turn had to ship them on to us once they got home. Those were something like $475 of wool.
It was clear that Filson only wanted to sell fashion items in Europe. Hipsters in lumberjack shirts being more lucrative than bushcrafters.
Filson are not the only company to have ranges which they do not sell in Europe. Keen shoes also do this, and that too pre-dates Brexit, and it doesn't matter if you are ordering in France, or in the UK, there are some shoes that are offered in the US that they do not distribute here, and KEEN US will not ship. In fact, they have agreements with some major retailers to prevent them from shipping outside the US too.
