Try get_iplayer. It's a Linux command-line tool to download the stream directly from the provider's servers. Despite it's name, it can get content from ITV Player and 4od too.
"The general aim of these science fiction writers is to frighten the people into a state of paralysis or psychological incompetence bordering on hysteria" – FBI informant
Hah - that particular show isn't even available on the catchup player! Assumed it would be, as I watched it/screen grabbed it live on their player. Oh well, people will have to put up with the shitty watermarked version I already have. It was utter bollocks anyway.