My guess is that, subject to planned maintenance such as service checks and scribe line inspections, the based fleet for any given base airport will not alter significantly, if at all.
When these maintenance checks are required, aircraft will 'tail swap' down route so the aircraft in question can spend a few days at Leeds or Manchester for a hangar input. For example, G-GDFT came into Leeds yesterday for the first time in weeks for attention in the hangar.