It’ll work for as long as there’s AM radio stations at least, they’re a bit of a dying breed in Europe although there’s still a few remaining networks of powerful national transmitters. The BBC just finished shutting down mediumwave local radio citing high costs per listener, though there’s a few hobbyist pirates popping up here and there along with noncommercial broadcasters like former offshore pirates Radio Caroline (if you haven’t read about those guys seriously give it a look, it’s a ridiculously cool story and very much in the hacker spirit if you’re into electronics). The longwave transmitter for Radio 4 will probably hang on a while yet I imagine though, hell hath no fury like English cricket fans deprived of Test Match Special.