Providing the right POD that shouldn't be impossible, but by 1945 your already hit with two big problems; France having it's shirt stuffed after the war and Britain already having it's guts tore out and thrown across the floor. By the end of WWII both France and Britain were propped up to be the European Powers, and France assumed the role of the continental master of the west. In reality France was in deep trouble for a long time (comparatively more so then post war Britain) to the point that, as I'm sure many people here know they even considered contacting the ASB's and forming a Union with the UK. Perhaps if France is treated as a conquered and liberated nation and Britain's position as her superior as an ally is made clear as day you might have a situation develop where the UK has the prestige and power to haul the EU in it's direction.
A few problems remain however; for one there's the empire that Britain is /still/ trying to preserve at least in some way (despite selling parts of her off, abet usually to friendly nations or dominions). Elements of Britain that would rather get rid of the empire I can't quite see being all to spun up on the idea of dominating European politics, and Frances position (both culturally and geographically) well put it as a natural leader (if not equal) in European Affairs; where as Britain has always had something of a disconnect from the continent.
Not sure about her abilities to do so, but she was defiantly the top European power for a long time following the war.