Re: Using 'Had better' in the past
I will fully own up to having previously "I didn't used to" because I it sounds the same as "I didn't use to." And that's an error, which I no longer make.
But I agree with my fellow American. We use "You better..." quite frequently on this side of the pond. "You better watch your step!"
In fact, the latter is in an Elvis Costello song, and he's from London. Granted, song lyrics are the bane of our existance. But here's one more: You better watch out, you better not cry, you better not pout, I'm telling you why: Santa Claus is coming to town.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.