all sorted now - managed to locate and purchase a new reverse pattern, control lever with adjustable microswitch from the guys at BikeSports Developments - £500 cheaper than a new fancy, strain gauge actuated quickshifter system - once I fix the old lever - I will add it to the FOR SALE section if anyone needs it!
I haven't seen a microswitch lever for sale for some time as most went to the strain gauge type some time ago I did see a old mechanical pull type brake switch connected to a reverse pattern lever via a spring on a 748 the other day, was plugged directly into the PC3 USB without any anti bounce circuitry in line, apparently it worked suprisingly well