Their Darkest Hour - Their Darkest Hour, #1

When alien starships from a hostile intersteller power arrive in orbit, Britain is one of their first targets.  Swiftly, the aliens take control of Britain's cities and force the remainder of the military to go on the run, condemned to fighting a brutal insurgency against a ruthless alien foe ... And, throughout the country, the ordinary citizens are forced to chose between collaboration or resistance, knowing that capture will bring certain death ...