Your son sounds like a credit to you @MadameBee.
It is only natural to feel apprehensive. I worried that DD wouldn’t have any friends, that she would have horrible flatmates and struggle to get back into studying after having a gap year. Luckily that wasn’t the case, and now she is in her second year house with some lovely friends, and achieved a high first at the end of her first year. We also have the fear of students getting ill, which doesn’t help.
You will find that as long as your son is happy then you will feel reassured that he is coping well, and this goes a long way to lesson the empty nest feeling.
That said, I slightly agree with @spongedog. The university Facebook page is full of parents who have been sobbing all summer at the thought of their young adults going away to university. This level of clinginess isn’t healthy. We don’t own our children, and it is so important that we learn to untie the apron strings. We need to learn not to guilt trip them into keeping in touch constantly because it becomes a chore. We need to let them fly, but at the same time reassure them that you are there for them.
From my perspective DD is an only child with not many friends at home, we are older and have no relatives nearby. DD needs to be independent because we won’t be around forever, hence my learning to let go comments. DD and I are very close, but we aren’t joined at the hip. As long as she is happy then I am happy. I did feel a bit flat when she went to university and did a load of decorating to keep busy.
It is possible to raise strong, independent young people and be happy for them to leave AND feel sad about it and miss them. They are not mutually exclusive.
I agree with you @OlegBurov