The UK collection of senior Archangels (four) & that area are involved in the end as well as having the oldest standing structure on Earth. I was born in Gillingham not far.
The nuclear shelter nearby is a death trap says God. The chalk pit near has multiple mushroom forms & a severed head with tongue. Defend the area anyway, less ICBM if they are shot down trying. It is possible but improbable that all of Russia's arsenal could be wasted trying. Plan for resupply on a network.
ICBM are less dangerous, praise God.
A pit like this for example could be defended within or atop using the edge for a 20% better chance of survival. Nearish top right corner of lower green square 30%. A maze with 50m width platforms beveled to 40ft from 50m high & 200m canyon would be very well defended. Dig a channel near steep hilltops, not straight.