Annie ........ since a few years ago, new windows come under Building Regulations standards. That shouldn't worry you because, I guess, you'll have a window company supply and fix. They'll knoe the Regs.
If they're FENSA registered, Building Control doesn't have to be involved.
You do need trickle vents under the Regs. I won't go into the detail here (you can easily Google it) because it depends on which room, how many windows in the room, whether the room has an exterior door etc etc ............