More likely that they would have followed the example of other friendly navies, operated Orion or Atlantique and now be introducing P8 into service.
Nope. Most likely (as large capital expenditure projects are invariably influenced by political rather than solely operational matters) the RN would have been pushed towards the same options as the RAF; whichever one promised the most jobs to UK voters.
If the purchase of the Orion or Atlantique had little UK workshare then the military's political masters would lean toward an alternative that did. To think otherwise is to display an astounding level of naivety.