Where the defence budget is magically going to find the necessary wonga to buy/rent/hire/equity share/steal/extort some shiny new MPAs is something of a mystery to me, but allowing for that possibility may I point out a somewhat bigger problem...
Binning the kipper fleet allowed the RAF to meet it's manpower reduction of 3500 posts, of which circa 1500-2000 would have been maritime-related.
Irrespective of who operates it, we is gonna need most of these posts re-established to regain the capability. And that is going to cost a bucket load of moolah...every year.