Well it's every one of mine for a start.
I can't pretend I'm familiar with British politics of the time (despite being British) but I would have thought Atlee/Bevin would have more of a mandate than a non-entity. They are not in government but this looks like a bonus now, with Churchill suddenly gone this administration looks more rudderless than Bismarck 1941.
One thing that does seem likely is whoever takes over will be less successful with US relations and the Soviets will trust them more.
So -
Duff Cooper takes over but vote of no-confidence after Norway brings in Labour prime minister of Coalition. This puts US help back significantly but greatly increases UK-Soviet co-operation. British/Commonweath land and air forces fight around Leningrad and Caucasus, from '42 Brit Armoured units forces have 6 pounder armed T34 instead of the M4..
Potentially the Tizard Mission goes East?
http://en.wikipedia.org/wiki/Tizard_Mission
all quite scary in long term