"The other point maybe someone can answer do all UK police forces contract out the pilotage service ?"
No. Some directly employ everyone including sufficient to cover leave and sickness. Some directly employ their Chief and Line pilots and buy in relief cover. It's down to individual forces and how they wish to balance the risk. Contracting can be more expensive but you are guaranteed cover - especially so in cases of long term sickness. Directly employed has it's benefits in that, providing everybody stays healthy, costs can be lower.