The bird automotive rack is actually very good, if expensive. It's a bit fiddly to get on initially but works really well after that. I have had one for a couple of years and swear by it.
http://www.birdautomotive.com/Bike%20Ra ... 20350Z.htm
Spotted one for sale on ebay too if you're quick...
http://cgi.ebay.co.uk/Bike-cycle-rack-f ... 286.c0.m14