I have just received an email from XBOX marketplace telling me that I can kit my xbox out for cheaper than usual! Contained within the email was a selection of links to external websites including Argos, Amazon and Game who all have a sale on their xbox accessories.
Some of the cheap products I found were:
Black wireless controller - 23.99 @ Argos / 23.97 @ Amazon
Wired controller - 17.99 @ Argos
Wireless microphone 5.90 @ Amazon
Wired headset 3.95 @ Amazon
These are just a small selection, I don't really have time to type them all up - sorry, but I will post a link to each site so you can rummage through the good prices!
Hope this helps someone.