As Allen said - you can use the EOS Utility program which came with your camera (using the USB cable to "tether" your camera and computer) - limits you to studio/home type stuff though.
The alternative is the
Canon TC-80N3.
They are horribly expensive here in Aus - I think you're looking at 100GBP (sorry, can't find the pound sign) in the UK.
Also remember that - depending on how many frames you're looking to shoot - your camera batteries might become a limiting factor.