The 7-up-like stuff is what I've heard called pub lemonade to differentiate it from actual lemonade. It's not the beverage of the whole nation, just a nationwide conspiracy of publicans. I'm guessing the cloudy stuff may have been Fentiman's.
I found out the hard way that Brits don't make lemonade as we do in the States (I ordered one in a pub and got something like 7-Up), but they do make a dandy cloudy lemonade! It's fizzy and full of aromatic herbs.