Best Physics universities in European
I know my way around the British university system best. Other answers cover the options in continental Europe fairly thoroughly so I won't deal with those particularly, though ETH Zurich is widely acknowledged as a particularly high quality institution. As an aside though, you should be careful about international league tables which are principally focused on assessing research. Look at national tables if you want to know about teaching quality.
Any serious physics programme will be able to train your brother in those disciplines. The best in the UK (definitely), Europe (almost certainly), and the world (possibly) is Cambridge - although you won't JUST be studying physics for at least the first year or two of the course: it's Natural Sciences which means you have to take a couple of other options (if you do, say, Computer Science and Materials Science alongside physics and maths it'll still be pretty physics-y). By third year you're specialised, e.g. in astrophysics.
As for the rest, well, people are sometimes surprised by who's in the top ten. Oxford and Imperial are of course there, and St. Andrews and Durham consistently perform well (Durham's largest department is physics). Edinburgh, Manchester, University College London, and Birmingham are very significant also. Those are all in the top 100 in the international rankings too, incidentally. Some of them however haven't quite built up the sort of international brand recognition that Oxford, Cambridge, and Imperial have though.