no caps, no FUPs. They used to have a 1TB FUP but they sort of tried to claim it was not really a cap but thats what you could get if you downloaded constantly. Anyway they removed that some time ago. They don't slow you down either. Used 1.2TB last month, still full speed. Of course it's a mobile network and is subject to being shared, capacity issues all that stuff.
As for FUPs not much you can do really. Yes we can argue that a 600GB limit on EE means it's not really unlimited, it might not even hold up if you go to court but I bet most of us wouldn't take it that far, we'd just cancel. But the ombudsman and advertising standards people do allow FUPs to allow networks to "protect" themselves but it must only affect 2% of users or less.
If you want real unlimited, the only network I know of that does it without FUPs or slowing you down is three.