From a pilot point of view, we have our standard calls, the last one of which on the approach to land is "DECIDE". As someone earlier stated, this could be at 200'agl on an ILS or 300'agl on an NDB or even approx 1200' on an SRA to EDI (!).
I have always thought about the decide call refers to whether or not we have got the runway environemnt in sight and that we are correctly aligned vertically and laterally.
If we forget LVP's - where late landing clearances should not be received - then so long as I could see that the aircraft on the runway was moving and likely to get airborne then I would not go around until I was in the flare.
We often get late landing clearances at CDG, about the only plac e I go to know, and have very very occasionaly had to fly below decison height before receiving "Cleared to land".
In contrast to BMI, there is no reference to when a go around must be flown in respect to a landing clearence.