One point that most (all?) credit card companies seem to be united on, and most borrows seem to miss out on (I know, I did once, painfully!) is what amount the card companies charge you the interest on each month; and Ratetarters might want to be aware of it. If you have spent, say, £100 and don't want to pay it all back this month but do pay, say, £60, you might expect to pay an interest charge on the remaining £40? Reasonable? No, not to the card companies! They will charge you interest on the full amount (£100) minus the minimum payment due (say, £5), making it that you pay interest on the £95. If it's Christmas and you have spent bigger numbers than in the example, the cost of not knowing about this little gem could be a nasty surprise come January. Hope it's helpful.
All the ones I've checked do it. And I've seen the same warning in the odd financial column of some of the more money-oriented paper publications. Now, as to is it legal, doesn't legality depend on how much you can afford to pay your lawyers? Or am I being naïve?