I can't speak for anyone else, but they told me they were increasing my payment to a particular amount (can't remember what it was), but that I could go into my account to change it - when I did it would only let me set it to about £30 less than they had picked, which was still around £50 more than I was paying.
They've "recommended" increased payments before (also badly calculated and ultimately wrong, but not imposed) that just ended up with me paying significantly less due to a massive credit balance, so as a result I decided to let it ride, but when I spoke to them I said that if I found myself in as much credit as I expect to be then I would be changing suppliers because I have no intention of going through this every bloody year.
Right now I think I'll wait for things to shake out, it's not worth switching supplier and finding myself at another one that goes bust.