You also have to ask what the age breakdown of the 39 + 113 is?
I believe that one of the 39 was 48 when he started the seedcorn programme. Therefore, extensions not withstanding, he has minimal longevity in any future UK MPA fleet.
Someone has already asked what the trade breakdown of the 39 + 113 is. I know of at least 2 ex Nimrod air engineers still serving, who would have no flying role in a UK MPA fleet.