Hounddog1 sums it up correctly, Kilfrost simply could not produce the stuff fast enough and they provide a majority of the fluid for the UK. you cannot mix fluid types in the same rig and changing fluid type requires the rig to be decontaminated from the old fluid amngst other things. this was a UK problem not an airport or handler problem. I should imagine Kilfrost are working overtime at the moment with the forecast of frost to the new year.