Interestedininfo - I am as ignorant about Physics as you claim to be - more so probably! and what I said about Oxford not having the best course is partly a superficial impression from having been round various Physics departments during Open Days, and partly relaying ds's very individual response.
Let's put it this way: the Oxford physics department is deep within the bowels of a building, no natural light, incredibly old fashioned in appearance. That's the superficial bit. The tutors were the least friendly and accommodating of all that we encountered. There was an undercurrent of 'we're the best learning institution in the world, what we do is the best, why would you question this? Our course has run for decades, why would we want to change it?' Most unis teach broadly the same things in the first 2 years, but some offer more choices for the students and more freedom to personalise the course to meet their particular interests. Oxford has the least choice of all that ds visited as far as I am aware.
From ds's pov, and this is obviously very personal, he has a particular interest in astro-physics and wants to spend a year abroad (Erasmus scheme or similar). I'm not sure about Oxford's astro-physics credentials, but they definitely are not interested in sending students abroad. It is a genuine worry for me that ds isn't being honest with himself when it comes to Oxford - if it was any other uni, I think he would have dismissed it on the basis of the course.
As for which unis are the best at Physics: I really can't say. I can only tell you the ones we considered.
Cambridge was rejected by ds on the grounds that he did not want to do a year of natural science.
UCL (which often comes out top in league tables for Physics) he rejected as he does not want to live in London - we have a close relative who suffered socially, being in London for uni. Ds likes the cloistered/campus environment.
Manchester - ds visited and did not like the city.
Birmingham - is on his list, but probably bottom at the moment as, again, the city does not appeal.
York - ds initially liked, but, having gone there a second time for interview, decided he did not like as the uni does not do research in astro-physics.
Warwick is good for astro- physics.
Ds also applied to Durham (not heard back yet).
He visited Southampton and I thought it was quite impressive but ds did not agree - I forget why. They certainly offered huge choice of modules for first 2 years.
Please bear in mind though that the above is just a mum's view of things. I think your dc needs to decide which aspects of Physics appeals most and look for unis that do research in that area.
I also take the unfashionable view that most unis are going to offer pretty much the same course as all the others, and therefore, liking the place you are living in is almost as important as liking the course.
Sorry, for long waffly post.