speedo readings

[Alfies bus]

hello there, i have just bought a 1971 bay blue/white which i am very pleased with, needs tidying on outside will be great when finished, but have a couple of problems to sort out,the main one being at the moment is that the speedo seams to be well out, when the speedo reads 75 mph i am probable only doing around 55 mph as told by someone following me, the same as lower speeds i never set of 30mph speed signs wilst doind 40 odd, I have checked the wheel size and they seam to be right according to service manual any ideas ????
also i am bl**dy cold at the moment I know they havn't got much in the way of heating but can anyone explain what all these levers do !!! :confused:

[Clem]

Try fitting a new speedo cable .... though a dragging one would normally indicate slower readings than fast. If not, fit a new speedo? Cheap enough second hand.

Re the heater levers. Keep the blue lever(s) in the up position, and the red ones down for maximum warmth ..... but dont expect too much. There could be literally tens of things stopping the heat coming through.