Sorties could take a couple of hours, Spitfires ranged all over northern France on escort missions. They also conducted "Ranger" (squadron free lance sweeps) and Rhubarb (section freelance sweeps) into France. A good book to read is Wing Leader by Johnnie Johnson or The Big Show by Pierre Clostermann. They both go into details about these types of sorties.
from the Spitfire V inwards they were also armed with Cannon. Cannon was tries on the mark II during the battle of Britan but they proved unreliable so a lot of 11 group squadrons went back to 303s