See what happens in Ireland with 5 aircraft covering 4 bases?
If you go for a spare option then you also need to generate a floating crew to position it when required, assuming your crews are pared down to the minimum required to comply with the EU working time directive.
People usually willing to pop in for a bit of OT when something needs re-positioning (another perk for you post-MilSAR
) assuming the WTD allows.