Are you all familiar with SDP/SI (Stock Drive Products/ Sterling Instruments)?   www.sdp-si.com     I have just received their set of  catalogs. Lots of good information in the Timing belts and pulley catalog. Almost one third of the catalog is dedicated to the technical information section.  You can buy long drive pulley blanks and machine them to your needs.  They also have a great catalog etc. on just drive components alone.  Bevel gears, worm gears and worms. You might find it worth checking the site.  I called them and asked for the catalog pack.  I don't know if they have a UK facility but you might be able to order the catalogs via the web.

Bill

Yep, good company, especially for the mechanical componets you need.