Is Sky doing something illegal?

I pay my bills pay invoice as I do not trust banks with direct debit. Now, I have a little behind on paying my Sky subscription but what I wasn't expecting this morning is that I turn on my television and my services are blocked. I call Sky to find out what is going on and explain that usually I have a two week "buffer" zone to pay the bill. However, and here's the good bit. Because I don't pay by direct debit, (which means they get more money out of me anyway for invoice charges) as of today, the 16th of July, not only do I have to pay my outstanding bill but two months in advance as well. No warning or update regarding this. Is this legal? It feels like Sky is penalising those who don't like to pay by direct debit and with all the rubbish going on with the banks I'm sure I'm not the only one. I couldn't believe it when I spoke to them this morning. I shouldn't even have been turned off in the first place because I still have two weeks to pay!!!