Since I discovered that the 40 ft refers to the height of the work rather than the height at which the operative works, I will have to adjust that on the next renewal.
Do it NOW if you have any work over 40ft - cos, sure as dammit, it'll be something over 40ft you'll have to claim for.
There's also something somewhere in your policy that says you have to inform them of any changes which might affect the conditions!