Originally Posted by
Archimedes
You might wish to look at
the RBL page and that from the
MoD.
Tankertashnav knows a lot about medals and may be able to advise; my take from the MoD page is that the decision to bury the medals with your grandfather would preclude replacement by the MoD, and that you'd instead need to find out the medals to which he was entitled and obtain a set privately. I'm sure someone who has far more knowledge will be along presently, but if not...
Forgive the pedantry, but you're asking for a duplicate set rather than getting them back - as well as offering some twonk the opportunity for an insensitive and inappropriate suggestion, it might imply to someone in officialdom that they might be in a position to be retrieved, which, of course, they're not. They are, in effect 'lost', even though you know exactly where they are (if that makes sense).
Unless there are any gallantry awards, WW2 medals are not named, a replacement set should be quite easy to source from a popular internet auction site. Expect about £25 for 39-45, Defence, Victory then £30-35 for Atlantic, France and Germany, Africa. A bit more for Burma, more again for Pacific and then £60+ for Aircrew Europe. The price would rise with documented provenance. If he was entitled to the Arctic Star and it hadn’t been issued, he (you) may be able to get that from the Medal Office.