IO540 "I don't know how Heathrow used to handle that..."
probably in the same way that they are as of right now - they are still fully operational, despite anything you, or AFPEx, may say or think to the contrary. IIRC, didn't you say previously that you've never used Heathrow FBU?
Oh dear, Pelagic, here we go again, you grinding that silly axe. You must be some trade union chap from Heathrow. What did I say "to the contrary"??
I've never faxed an FP to Heathrow but from what I have read/heard, most UK airports have been faxing FPs (filed at their towers) to Heathrow. Mostly VFR ones, that is.