When was the last war between France and Britain?

The French Revolutionary Wars and the Napoleonic Wars (1792-1815) at the conclusion of teh Second Hundred years war where the last wars between teh UK and France.

https://en.wikipedia.org/wiki/Wars_involving_England_and_France

Strictly speaking, we last fought a proper full scale war with France in Napoleonic times. However, after the fall of France in 1940, Britain was technically at war with the bit that came under Nazi occupation....particularly the navy. When it refused to surrender, the Royal Navy sunk much of it to stop the Germans getting hold of it.

https://en.wikipedia.org/wiki/Attack_on_Mers-el-K%C3%A9bir

Although there was not a formal declaration of war British and French forces did clash a few times during World War 2. Germany occupied part of France. The unoccupied portion became a puppet state known as Vichy France which was sympathetic to the Nazis.

As mentioned by mikew41 the British bombed the French fleet in North Africa to prevent the possibility of the ships being used against the allies.

In 1941 the French supported the Iraqis in their revolt against the British. The allies (including Britain) responded by attacking French held Syria and Lebanon. Britain was also involved in the allied invasion of French held Madagascar. In November 1942 Vichy French troops resisted the landing of allied troops in North Africa.

https://en.wikipedia.org/wiki/Axis_Powers#Axis_collaborator_states
https://en.wikipedia.org/wiki/Syria-Lebanon_campaign
https://en.wikipedia.org/wiki/Battle_of_Madagascar

Operation Torch, November November 8.-10.1942 might have been the last clashes between (Vichy-) French and British troops.

https://en.wikipedia.org/wiki/Operation_Torch