Except most people overseas can't see the advert, let alone the content. Some of the content ends up on Netflix, allowing them to tie up even more of the global market, and some of it is viewed for free (e,g, via a VPN) but most of the BBC's content simply isn't available outside the UK. And...
Good. Hopefully the BBC can move to a decent subscription sevice and flourish globally, instead of having to geoblock everything outside the UK, while forcing everyone in the UK with a TV to give them money or face being fined (regardless of whether they view BBC content or not).