British forces landing in the devastated Glasgow as part of the operation to clear the City as the UK government expanded its Safe Zone. Eventually the Wall would stretch from Newcastle to Gretna Green.
Although the bulk of surviving UK forces would be based in the Scottish Safe Zone, significant ground forces where deployed to keep Ireland (all of it), the Isle of Man, and Isle of Wright Zombie free. The Royal Navy and Army dominated over the Royal Air Force, with conscription brought in to bolster numbers and give survivors something to do.
Abroad the UK managed to keep the Falklands, Gibraltar*, Ascension Isle, Bermuda, St. Helena, and the Pitcairn Isle. Most of the Carabean isles had to be abandoned due to their close nature seeing 'island hopping' zombies. British Indian Ocean Territory was lost after it was overrun with survivors from mainland India, and the virus. Tristan Da Cunha survived for over 5 years until an Cruise Liner grounded in Stoney Bay and slipped hundreds of zombies onto the island. Due to its inhospitable nature, the islanders had time to exec before they where overrun.
*The Battles for Gibraltar would be the subjects of several movies, and documentaries over the years- even the monkeys learned to stone zombies in the head.