I think you are being a bit unkind there. There aren't all that many institutions whose name is known internationally. Oxford, Cambridge, Harvard, probably another 5-10 US ones...and then the list sort of peters out. Most people probably can't think of a really good French one (and not the Sorbonne, which isn't all that) or German one or Italian one but of course these countries all have some excellent places. Moving further east, Charles and the Jagiellonian are centuries older than most.
So yes, I have heard of ETH and am well aware that it is at least as good as all but a slack handful of UK institutions. Whilst I wouldn't really expect John to have heard of it for the reasons mentioned earlier this is less reflective of the standing of the institution than general ignorance. This is not something shared by all as some have lived, worked and studied abroad or with people from other countries.
PS Jiao Tong rankings have ETH in 27th place, just after UCL. If needs be, perhaps you could put some sortof comment in about "leading Swiss institution, placed just after UCL in global ranking" or something. Dunno, may be worth a try! Question then is whether something below UCL is of any interest to them!