Hi Simon,
I bought a set of these extension tubes for my EOS 20D a few years ago and they are excellent.
There are cheaper alternatives around which don't have the contacts to allow the auto focus and through lens metering to work, but certainly I would recommend these.
If you can wait until the 9th of June I could meet you at Fleet services on my way to the channel tunnel, and you'd be more than welcome to borrow them for a week to see what you think whilst I'm driving to Rome and back....
All the best
Richard