It's an FPS-RPG.
A radioactive wasteland consisting of the whole of England, every city mapped out in immaculate detail. *with obvious changes made due to nuclear holocaust, resettlement, conflicts, etc.
The radiation has zombified the majority of the population, and the rest have now arranged themselves into factions:
One, would consist of scientists being guarded by a military of sorts, attempting to create a method of fixing the irradiation and a cure for the mutations (Think BoS in the Fallout universe, minus the advanced tech.)
We'd then have the stragglers, the survivors who were neither military trained or intelligent enough to help the scientists. They live a half life, scattered in isolated towns and cities, dwelling in the mountains, farming what they can and raising livestock.
They are constantly being attacked by the Wildsmen, the ones with corrupted senses of morals, finding it easier to steal than to create.
All of these groups are being attacked by small divisions of mercenaries from overseas, attempting to steal money, food, land, and technology.
There are also unconfirmed rumours of something inhuman living in the ruins of London. For the time being, we recommend avoiding the city and its suburbs - if nothing else, many of the mutants roam the area.
Now, I realise you're probably thinking "oh, he means the english fallout 3".
Sorta. But not. Fallout 3 couldn't quite satisfy me - it was too small. This game wouldn't have the giant piles of rubble from the DC ruins that couldn't be climbed; all buildings would be accessible, the only exception being the channel tunnel, which is cordoned off by the french military.
The game would have random encounters - maybe sometime you'd wander into a town previously thought of as safe, to find out that Wildsmen had burned it to the ground and taken everything.
The game would include a variety of mechanics I don't recall seeing frequently elsewhere - hunting, tracking, making shelters, a decent economy..
The combat, being set in England, would be forced to rely mainly on melee weapons and explosives, although there would be a variety of trapping methods thrown into the mix, especially when sheltering in a building.
It would be possibly to destroy the majority of scenery, providing it wasn't mission critical - would be possible to blow up a house or similar buildings in order to kill your foes.
There'd be an abundance of cars, but parts would need to be found in order to fix them - the strikes on England knocked out the majority of electronics.
Whoa crap I've wrote a lot. I enjoyed that.