I am not sure just why you can't change the speed limiter.
That it is a canbus system doesn't make it fixed and unchangeable. Its the ecu communication format (more or less)

So far as I know my thruxton and t bird are can bus (1600 t birds always have been) I have changed the limiters in both using tune ecu.

I would suggest getting cable and plugging in. If you can see the speed setting,then you can edit it. Unless there is some UK restrictions that I am not aware of.

05 speedmaster - 1100cc, 11:1 racing pistons, Carillo rods, thunderbike cams, ported and polished head, 2mm over intake and exhaust valves, Barnett kevlar clutch, scepter pipes, oversize manifolds, 45mm HSR's, TTP stage 4 firestarter