"Cost is likely to be the answer to my question but have NPAS got RNAV approaches setup to their bases?"
You are correct....it is extremely expensive to have an Rnav approach approved for an airport. As most of the Npas bases are at airports it's down to the airport operators/owners to pay for them, it's nothing to do with npas!
However, there are Rnav approaches at; Birmingham, Doncaster, Exeter, and Newcastle for NPAS to use....if you have an IR with a PBN endorsement?
B.