During the seven years war (1756-1763), britain's main ally in europe in its war against france was:

During the seven years war (1756-1763) Britain's main ally in Europe and it's war against France was the Electroate of Hannover and Prussia.

Britain's closest European ally, the Netherlands, stayed away from the war and were able to maintain their neutral position.

The war was the biggest of its scale uptil that time with more than 600,000 killed and being fought in 5 continents around the globe. It is often called World War Zero and by some as the original World war.