KentSlimm: UK universities don’t have gen ed requirements full stop. You apply to study one subject (or occasionally a combination of two, or even more occasionally three), and that’s all you study for your three years.
Most places will welcome US students - St Andrews in Scotland has the biggest reputation for being extra-keen to recruit Americans, but I’d look more widely.
CS isn’t really my area, so I don’t have any specific recommendations. It may be worth posting in the International or Study Abroad sub-forums here to see if anyone has personal experience of CS, or there’s a UK equivalent called The Student Room (google it, we aren’t allowed to link). I suspect he’ll need to look carefully at the specific courses especially if he has any particular interests within the field.
Most University websites have helpful pages for international applicants giving general requirements for admission, but bear in mind that you also need to translate subject-specific requirements into US qualifications.
What are your son’s stats? That will dictate his options.
Here’s one top 10 list: http://www.telegraph.co.uk/education/educationpicturegalleries/9601080/Top-10-universities-for-computer-science-and-information-systems.html?frame=2366023
It puts Oxford at the top, and that is very competitive for admissions, as you can see here:
Here’s an overview of the course at Oxford: https://www.ox.ac.uk/admissions/undergraduate/courses-listing/computer-science?wssl=1
However, it may involve a bit too much writing to suit your son, which underlines my point about carefully reviewing all the courses he’s considering applying for. The UCAS application system only allows you to apply to 5, so you need to select carefully.