Yes, pilots could get leave individually; fighter squadrons had (in theory) more pilots that aircraft though actual numbers (of both) varied considerably. The Initial Establishment (IE) in 1940 was 24 pilots and 16 aircraft. A full squadron typically flew 12 aircraft (two flights, 'A' and 'B', each with two sections of three aircraft), so there was scope for aircraft maintenance, pilot sickness and leave etc. Of course in practise things varied: "... actual strength, rather than establishment, could vary from 12 to 20, whilst the number of serviceable aircraft was even more variable" (Ken Delve, Fighter Command). At the height of the Battle of Britain Fighter Command had insufficient pilots for a full establishment of 24 per squadron, but tried to keep at least 19-20 operation pilots in the critical squadrons in the South East bearing the brunt of the fighting, so even during the heaviest fighting RAF pilots could get some leave.

Squadron Leader Tom Gleave, 253 Squadron: "You had a situation in which a couple of men might be on leave, two chaps were in the station hospital because they'd got shrapnel in their arms or some place. Group Op would call and ask, 'What have you got?' They'd be told, 'We've got three aircraft and two pilots or four aircraft and three pilots.' You'd be told, 'Put a defensive flight around the aerodrome, just in case.' You'd take a couple of sproggs [new pilots] with you because they might be the only ones left on the ground."

Sergeant Paul Farnes, 501 Squadron: "The only reason I lost my Hurricane was because I went on a 24-hour pass. I lived in Worthing, which was easy to get to from Kenley, and I went home for the day. It was 15 September and a Belgian pilot had joined the squadron. I’d never met him but he was apparently given my aircraft to fly because he wanted to or they needed him to fly so he was given my aircraft because I wasn’t there."