Radio 3: yes (it's on BBC's multiplex).
Classic FM: no, it is not on DVB-T, only VHF FM and DAB as far as I know (for which you need a DAB radio).
NPR: not a chance. Why would that be carried on UK TV bands?
There is a rider to this. There is access to Internet Radio via an Internet connection and the Humax portal. A search for "NPR" shows up a few listings, eg "KAXE NPR 91.7 FM". Classic FM shows up too.