Have you tried this? http://www.copperbed.co.uk/
Courtesy Helen Yem in Telegraph's Gardening.
i like this idea but as I'm not working any more i can't honestly afford it at this time but five years ago when the garden was in its infancy and i was throwing cash at it like rain ::) i would have bought it, i did go down the copper tape route but found it a little to sharp and injury causing so removed it from my beds.