I think you have to let him know you are there OP and be as involved as he will let you. I was concerned by lack of revision in Year 2, so threatened to drive to the UK with a sleeping bag and camp out in the sitting room of his shared house to ensure revision, proper nutrition and to take the PS4 away.
Ds got the message and a First for his BA.
I know when something is up as he will ring me to talk to a real adult (his words) and there will be something in his tone that I pick up on. I do whatever he needs, from reading essays and making suggestions about paragraph order, thrust of the argument etc, to proof reading his dissertation, or being a general sounding board for things.
Ds was away from 16, as he went to sixth for in the UK, so university wasn't a shock to the system. What does floor him at times is the whole notion of being adult, and the myriad of things this entails. Mind you, that still gets me at times, and I'm 52. I think that we are so used to being adult and dealing with all the stuff one has to, that we forget this is the first time for them. I remember having to explain how to pay the water rates, and the gas bill to him, as he had never had to deal with any of that before. It can be things like that, which to us are second nature, that trips the kids up.
Ds is currently doing his MA, and I still have to kick him on the occasion to get his arse in gear. He talks a good game, but turning that into action is sometimes his problem, as is the inability to have two or three things on the go at once.