At the full extent of the Lightning's combat range, it would be capable of around three passes on target. The first would be able to attack two targets with it's missiles, and the other two would be against anything else in it's area of attack. If really needed plenty of tankers would already be about somewhere, if not the single Lightning can go home, but there's always the rest of the squadron to follow which would already be up in the air by the time the first (most likely two) would have to go home.
I'll have to ask my dad about doomsday scrambles, but they could have RAF Binbrook empty of all operational Lightnings (about 24 normally) in 20-30 minutes, maybe less. During that time others would be coming home, being refuelled and rearmed then sent back up.
And pilot gunnery training over Cyprus kept RAF pilots in tip-top shape for gunnery. My dad saw plenty of 'targets' splattered by firing Lightnings over the Med.