What were the advatages for British fighting the battle of Britain?

Radar

Alternative answer:

As much as having radar was the use it was put to - it was integrated into a reporting system so that fighters could be directed where required.

Another advantage was that it was fought over Britain itself - any shot British pilots were already home, any shot down Germans were captured.

German aircraft were at the maximum extent of their range (especially the fighters) and had limited time before needing to turn back, British aircraft were mostly operating within mere tens of miles of their home bases.