Right, all the cities within the black line, can try get to the coast, but that would be difficult. I reckon most people in Greater Manchester and West and parts of South and North Yorkshire could go to the pennines. Apparently, zombies aren't great with heights. Places like Birmingham would have to coordinate themselves to get to as greater height as possible. Other places will fill up local swimming pools. It sounds stupid, but a zombie couldn't swim. Water would be crucial. Once the coastal areas have been cleared, the army (yes, the army) come to the rescue. They would start shipping people out to sea.
It's not a complete plan, as I've got to go very shortly, but I'll fill it out a bit more when I get back, and I'll answer questions about it then.