Allied forces land in France on D-Day and German V-1 planes fly in UK during World War II

The V1 Buzz Bomb, a terror weapon, was launched by the Germans in an imperfect state, targeting London and the English countryside for 80 days. The Allies eventually drove the Germans from their launch site. Fortunately, over 75% of the bombs were either shot down or failed to detonate due to internal faults.

What was the state of the V1 Buzz Bomb when it was sent skyward?

What could the Allies do to the Germans regarding their launching site?