BBC iPlayer Radio is free to listen to outside of the UK; it's BBC iPlayer TV that's region restricted. Unfortunately, this is very confusing for people because it's basically the same website. As an example, Neil Gaiman was trying to spread the word about one of his books being read on BBC Radio 4 recently and was met with a torrent of "but isn't that only available in the UK?" questions. No good deed goes unpunished.
I'm in the US and I'm addicted to Radio 4 and Radio 4 Extra. It's the perfect antidote to being bombarded by US political turmoil in our news (I kind of find other people's
political turmoil interesting to listen to).
In a more on-topic note: I was delighted to see that Radio 4 Extra playing the radio play version of Stephen Baxter's "Voyage" this week. I know there are many Voyage fans here. The acting is a bit ham-fisted and the American accents are not very good but after listening to the first episode I think the basic guts of the book are there.
For those that are not familiar with iPlayer Radio: Episodes are usually available to listen to for 30 days after the broadcast date. Here's the page where you can find the available episodes of Voyage: http://www.bbc.co.uk/programmes/b00lh6t1/episodes/player
I highly recommend the BBC iPlayer Radio App on iOS (it might also be fantastic on Android too, but I've never used it).
Speaking of Stephen Baxter, he was also briefly a guest on another Mars-themed show this month where they visited the real-life locations from H.G. Wells' War of the Worlds and discussed the context and backstory of the book.