I suspect that will depend on how long the AAC want to keep operating the N3 - maybe Pumas for 658 as well then?
They're MOD assets anyway, unlike the 412 and 212 which are contractor owned. I'd imagine they could find a way to get another maintenance organisation in and TUPE the staff over if they had to, keep the N3s ticking over until the new meadium-lift Puma replacement airframe is in service.