Well.
My airline, (KLM) has centralised load planning.
And we have LMC's as well. But they never cause a blockage of a taxiway. We wait for the final figures and won't push back without them.
I would grill the BA crew ahead of me via the radio if they wouldn't be ready for departure within a minute or two.
Blimey: And BTW KLM also lands on 18R, as you very well know...you don't seriously think that thát would be normal policy in over-correct holland would you?