<<Judging by your name you work for Ba in which case you might have noticed that BA dont normally use in excess of reverse idle>>
I do, and no we don't... However, there is the well known saying "Dont' s**t on your own doorstep!".
We know LHR well, even when tired. We know well where xyz autobrake will stop us, and we have company SOPs re more than idle reverse (i.e. try not to).
Elsewhere, when tired / less familiar (and we can be talking local knowledge like slippery areas rumoured at BHX, CGN etc.), I might be more likely to tend towards full reverse. So same with "visitors" to LHR... I suspect these visitors are also tense about reams of notes about minimum runway occupancy etc., and full reverse might help you get a better choice of runway exits...
<<as has been requested by the authorities>>
In fact, the wording is now used at nearly all airports, so the impact is lost somewhat...
Finally, it gets very un-PC to "push" non-use of Reverse Thrust. Qantas @ BKK saw to that! So airlines and maybe even airports are wary about over enforcement...
NoD