I rather think flightcare are provided with a concentrated fluid which is then thinned out by them, so it's a pitty indeed that they have run out of stock so soon.
Hahaha this is a good one. A concentrate that is thinned out, like orange juice from concentrates.
It gets mixed with water at application, but it never gets thinned out my friend.
You de-ice with hot water or hot type 2, or infrared like at some airports, then anti-ice with type 2.
Or you can de-anti-ice with type 4 with shorter hold-over times. Or de-ice with hot water and anti-ice with 100% type 4 with longer hold-over times.
Take note, because it's a shame for a pilot not to know this, especially since you have to suppose that the anti-icing guys can give you the wrong data for you to reference on your hold-over time table and you should be able to detect that something may not be right.
Hold-over times are longest with type 4, which is the most commonly used one in Northern Europe.
Major supplier of the product is kilfrost.
Technically speaking, SN could still AOG the fluid from somewhere and offer it to the handler for their use only. It would seem to be a lot cheaper to do that than to ground all the fleet for 2 or more days right before Christmas.
But if they elect not to do that, it means that it doesn't add up financially or logistically.