So, being a tea-swilling imperialist Brit, I have been giving some thought as to how to apply Red Markets to the UK. I know Caleb talks about doing more setting material as a stretch goal, but shh, I'm impatient.
So, the first aspect I wanted to grapple with was what the UK's Missippi is. That is, the dividing line that would split the Loss from the Recession. We don't have any Mississippi-tier rivers but the big geographical feature to divide the country would be the Pennine Mountains, which more or less run up and down the centre of England like a spine. It wouldn't be a perfect barrier, they're far from totally impassable, but there's pretty dangerous moorland and tarns up their for zombies to fall in and die, so you wouldn't be getting more than a trickle through.
Bringing socio-economic class into the mix, you could also go for a North/South split. Essentially the North of the UK and the South are very culturally and politically different, with the South having more money and political power (especially the South East, where London squats and distorts the landscape like a huge, grimy toad); healthcare is better in the South, property prices are higher, local governments have more authority, good luck trying to get anywhere in literally any art or creative platform if you're not in London. Of course, "the North" is also a very contentious and poorly defined area without a clear boundary and there's a lot of debate as to where "proper North" is, but it is generally accepted to include The North West (the Lake District, the Peaks etc), the North West (Northumberland, County Durham etc), Yorkshire and the Humber, Scotland and Northern Ireland . The Midlands, of course, are the boundary, but given West Midlands have some of the most economically deprived regions in the country it might well be that "the North" now basically means everything north of Cambridgeshire.
London itself, being a huge and very socio-economically divided city, probably got "interesting" during the Crash. It's one of those cities that is actually just an amalgam of multiple cities and towns sprawling out to meet each other, so I'm imagining that it might have just split back along those old lines. Some boroughs would fall but London has enough money in it (by some estimates the largest metropolitan economy in the world, with a per capita equivalent to Iran or Sweden) and is the centre of power such that a lot of soldiers probably die securing at least the nice bits of it. A lot of foreign money has been pouring into the city (a lot of dirty money especially) buying up property, meaning property prices have been spiking in recent years and pushing people to the outer boroughs; so you could turn that into inner London being the formal "settlement" with walls, guards and spotlights, and outer London being more wild-west. Alternatively it could be the opposite; the inner city is too dense and tunnelled-through by the Tube to meaningfully hold defensively, so the government falls back to the outer boroughs and a common Taker job is delving into the financial districts etc to reclaim deeds of ownership, business transactions etc going on in The City - with all the money that passes through London, a lot of it might would be interrupted and frozen by the Crash so naturally people might want to get their hands on, say, the land deed to some farmland that just became way more valuable.
There's also the issue of, well, guns. Can't have a zombie apocalypse without shotguns! Well, the largest groups of gun owners in the UK are the military, the police, the crooks, the farmers and then (distant fifth) sports shooters. BUT there's a lot of industrial infrastructure still lying around Up North and in the Midlands where guns were made in the good old days and could be made again. A job could also involve a run on the Royal Armories in Leeds, which is basically the "spare" Tower of London that doubles as a military museum of arms and armour.
