Hi
In your post it shows that you're still using flvstreamer.
So it's an old version of get_iplayer, I think.
RTMPDump is used now instead of flvstreamer.
It would be better if you did a clean install with the latest version of get_iplayer.
From here:-
w  w  w  . i n f r a d e a d . o r g / g e t _ i p l a y e r / h t m l / g e t _ i p l a y e r . h t m l
When you've done that, the commands will be:-
For 1280x720:-
get_iplayer --get --mode=flashhd --pid=XXXXXXX
And
If there isn't a 1280x720 hd version available... 
For 832x468 try:-
get_iplayer --get --mode=flashvhigh --pid=XXXXXXX
Or
For 640x360 try:-
get_iplayer --get --pid=XXXXXXX
When they're downloaded the files are type mp4 format.