Cheers Simon, it certainly freed up a lot on the journey, but I think you're right about the geometry being a bit off.
I've dropped Mike P an email to see if he had a similar problem with the speedo, and also dipped a toe in the water with speedycables to see how much a recalibration costs. Did the box come with a speedo drive? I'll email Burton and see what specs they provided.
I got Speedograph in Nottingham to re-calibrate a vintage Smiths tacho I acquired. This involved an increasing gearbox mid cable and a custom dial. Sorting your speedo drive would be a simple task for them I imagine.
