My advice is stick with a Western Digital, ive had them for years, very hard wearing and reliable, also dont just go for the cheapest one you will end up loosing all your data for a few pounds :)
Instead of downloading it through the desktop program download them on line they should go strait to your Iplayer desktop
go to http://www.bbc.co.uk/iplayer/
go to the required show
scroll under the video
click "download options"
then "for iplayer desktop"