I know the British offices of STA Travel and Campus Travel offer various air passes. Lufthansa, Air France and Alitalia are the main ones that offer these. Some of these are restricted to educators, students and ISIC card holders. Lufthansa would clearly be the best bet for you if you want to stick to Star Alliance carrier. Post a reply here is you want their details.

BA and British Midland also offer passes to the general public. Check out the business traveller site - they had a recent article on air passes recently. Their web site is http://www.btonline.com/cgi-bin/frontend.cgi?showlink~usbtonline~reports~100024~~

British Airways publishes an interesting brochure on its air passes - call them at 1-800-AIR-WAYS to get it!

You should also try contacting large London travel agents like Trailfinders - their web site is http://www.trailfinders.com - and Flightbookers. They may be able to offer you cheap one-way tickets.

Hope this helps ...