Given the choice, my husband would look for Russian, German or Eastern European gear when he is at a military surplus place- the Irish gear is not bad either. Just harder to get. But we need stuff that manages cold and damp, not desert terrain. I remember years ago in the UK the British military stuff was poor quality, not sure if it's changed. Probably not, as governments are investing in technology, not equipment.
Thank you for the list
@Hardcalibres
Russian military gear works in the cold, but it is also made down to a modest cost and so is bulky and heavy. It restricts your movement and capability and is somewhat uncomfortable too.
The really good gear can handle a very wide range of conditions - many people think that places like Afghanistan were just hot deserts......but the winters there were very cold too.
The gear on the list I posted will handle cold/damp.
I have a layering system made by Beyond clothing that I have used to work in at -60C (-72F).
My Wild Things Tactical Expedition kit would handle about -20C (-4F).
I have worked in Crye Combat shirts and pants, while wet, for days.......three layer goretex shell clothing from Wild Things, Beyond or Arcteryx is as good as any wet weather barrier layer made anywhere in the world.
Just don't expect the very best gear to be made from heavy fabric that lasts for years.......that is not a priority for the military. If it gets torn or worn through, the military has a big pile of replacement items sitting somewhere ready to go. Fabric choices prioritize performance and maintaining full range of bodily movement.
The other bad news is that the military orders for that sort of gear have mostly dried up........so not as much is being surplussed out anymore. It is a lot more difficult for civilians to find now than even five years ago.
Edit to add: Yes the UK military gear is still about the worst quality of any NATO nation. About the only exception to that was boots. They were and (AFAIK) still are issuing Meindl German made combat boots that are very good.