Spain and Portugal:
Portugal produced a local version of the G3 starting in the mid-1980s, as well as MG-3. And of course 7.62N ammo to go with it.
Spain (I never quite understood the supposed reasons for Spain to fall apart completely in any canon, though I can see falling back to regional levels. Regional govt + factories + ports hmmm) produced not only small arms, but IFVs, including supporting artillery.
Spain produced an indigenous AR design (CETME model C) in 7.62N starting in 1974, replaced by an improved action in 5.56N starting in 1987. And the MAG3 MG. As well as local production of mortars and artillery, and both IFV/APCs and soft-skinned military vehicles.
So, Some amount of weapons and NATO-flavored ammo may be available in the UK nearer than Japan or Brazil.
Brazil it self is an interesting case, as even if you strike its oil industry targets with small nukes...
- It's a large enough place that a few strikes will not destroy all of it.
- In this period, it was taking strides away from oil dependence, including creating industrial ethanol production.
- It had a fairly large industrial output, including softskin and IFV, APCs and tanks.
- It had agricultural output enough to cover its population.
Argentina is also in a decent position - except as far as I know, they had not yet made an ethanol industry...
More on that in another topic.
Uncle Ted