I've failed to get iplayer to work with gnash - and indeed have been avaioding the beeb entirely recently because something about the video they put on news articles kills epihpany-browser/firefox completely. So I was miffed when the old radioplayer got turned into iplayer so I couldn't use the radio either with free software.
However I did discover the beebotron recently: http://beebotron.org/ which gives lovely simple links to ram files you can play with whatever you damn well like instead of having to jump through the multi-layer hoops of iplayer (have you looked at the code for it? - it's monstrous). (This is radio only, but that's fine by me).