The only re-fuelling training done by the crews is generally done in the bar when the alcohol level drops
But to be fair, the Merlin has some pretty long legs anyway, fit an extended range tank down the back and you can go an awfully long way for a helo. So it already does pretty much everything it needs to do for the time being.
Being fitted for AAR would be handy if the JPR side of the house ever gets re-established, but again, you would then need suitable tankers to refuel from ... Merlin might be a nippy helicopter, but it won't be keeping up with the VC-10s. And as we can't even get the replacement for the 10s sorted out, I don't think we will see a Merlin specific refuelling capability for a long time if ever. But I'm pretty sure that the AAR capability was something pushed quite hard when we tried to flog it to the US as part of the CSAR-X programme!