So I'm always watching DVDs / internet streamed content on my laptop, which has a 15 inch screen. It's fine I guess, but it'd be a bit nicer to have a larger screen for watching films etc. What's my best cheap option for getting a screen that's say 22 or 24 inches?

Regular external monitor? Some sort of new-fangled television with the appropriate cable? I don't currently have a television of any sort and don't really want to spend a lot of money on this (in fact I'll probably just buy something secondhand), though I'm curious about any price-point quirks (ie prices disproportionately cheaper for certain size ranges etc).