This is not specific for computer science at all but my dd has just applied for university (current year 13) and this is what she found helpful.
This website:
https://www.theuniguide.co.uk/used to be called Which? Uni. She found it really helpful to draw up a "longlist" of universities that she thought might work for her - she put in her course and her likely grades and then it gives a list of all universities which offer that subject with similar grade requirements.
Once she had the longlist she went on all their websites and looked at the content of that degree subject at those universities (I'm not sure about computer science but she found that the courses she was looking at were really quite different between different institutions - I'm guess computer science will also have a lot of differences).
This then resulted in a shorter list. She then looked at the universities themselves (online - this was all over the year 12 Christmas holidays when we assumed we would be able to go to real open days! - she just went on their websites) and decided on things she liked (city university) and didn't want (campus university). This caused some significant decision making eg did the fact that she loved the look of the course at Exeter outweigh the fact that it was on a campus? (the answer was no).
She then came up with 6 universities which we planned to visit. We then did the virtual open days for all 6 of those when open days were cancelled.
(The first part of this she did on her own; we did as many of the open days together as we could as that had always been the plan - weekends away to visit them).
I don't think she would have engaged so well with the virtual open days a whole year in advance - it feels so much more real now and felt so much more remote to her a year ago. But of course some children might want to go to them early.
That website above was the best thing we found in managing to get from "100 universities offer this course, how do I start to narrow it down?" to "OK I have a sense of what I am looking for.")
Hope that helps.