70 Quid shipped seems to be the going rate for a 320GB, so it is only 20 dollarpounds difference between the two solutions, I can spot you that.
Also, with your dead external drive, if it is a Seagate contact them directly and they will absolutely replace it.
If you don't know what brand it is open it up and it will probably be a seagate or Western Digital drive inside, and you can contact Seagate or WD directly to get the drive replaced under their warranty, you can do it right on the seagate website - you just pay postage.