I have a dc studying in Germany, on an undergraduate STEM programme taught in English. Dc is having a great time! The course is super-international with lots of students from all over the world, but obv all speak English. They have the opportunity to learn German as part of the course. There's less pastoral care and hand-holding than in UK universities, so they do need to be quite self-motivated and resilient.
Public universities in Germany charge no fees - they do have to pay a 'Semesterbeitrag', which is a contribution to student services of around €250 a semester (ie. €500 a year). But that gives them a student card which entitles them to subsidised catering and sports facilities, and also counts as a public transport pass, ie. free public transport in the whole region.
Overall cost of living is much lower than in UK - DC's rent is €260 a month including all bills for a large sunny room in a hall of residence. Private rentals are a bit more, maybe €350 a month plus bills. This is in a large busy city, but not an expensive hotspot like Berlin, Munich or Hamburg. Halls of residence spaces easy enough to get as long as you apply early.
DC has joint Gm/UK citizenship so is entitled to German student finance, which is a much better deal than the UK version - the total amount they receive is roughly the same, but only 50% is repayable, and that is at 0% interest for the duration, with the rest as a grant. Non Gm citizens wouldn't get student finance, and I've been told you have to prove that you have sufficient funds to support yourself, ie. you have to show a specific amount in a blocked bank account when you apply for the visa.
The application process is quite admin-heavy, and a non-EU citizen would need a visa, so you wouldn't be able to start studying in the same year s you did A-levels. We did manage it by the skin of our teeth, but if you had to apply for a visa as well it wouldn't be doable in the time.
Would highly recommend - obviously the T&Cs vary across different EU countries, but there are increasing numbers of programs being run with English as the language of instruction (although apparently NL is cutting back a bit out of concern that Dutch is being squeezed out?). But if your dc likes the idea of getting a really international perspective and potentially coming away without the huge debt burden of UK higher ed, then it's really worth considering. They may never want to return to living in the UK though...