Sounds like he needs a wake up call, and needs to face a future where he doesn't go to university.
If he's lazy and a gamer, how will he adjust from a fee-paying school, where there's usually a lot of spoon-feeding, small classes, and individual attention, to a university in a subject such as CompSci where there are large classes and you're expected to be self-motivated & work independently?
He needs to contemplate this. And think seriously - is he suiyed for academic study? University is not for everybody and it's not a middle-class finishing school.
Maybe he needs a gap year (at least a year) in which to grow up & take responsibility.
I think sometimes parents, schools, and the children themselves, get on a sort of treadmill about school, A Levels, University, without really thinking about whether the child is suited to university. It's not compulsory, and there are other things he can do, if he enjoys & wants to make a living out of working in the digital world.
How about BTEC (which is much more hands on & not so academic), and a modern apprenticeship? When he's more responsible and mature, then he can go to university if he wants (or needs) to.