You can also be prosecuted for careless/dangerous driving if you
go round a corner too fast but lower than the speed limit.

But the manufacturer's limits are much better defined than a speed round a
corner, so although they would be prosecuted under a general provision, the
offence is likely to be accurately determined by your failure to comply with
the manufacturer's recommendations. In fact, your failure to do so can
probably be measured more accurately than your speed!

Christian.