The parent is talking about subway "trains" (sets of coaches, with each car having its own small electric engines, all powered by a common third rail); not, er, train trains (vehicles that pull themselves along two rails using a locomotive.)
High speed aside, in the UK, i think pretty much all inner and outer suburban main-line trains are electric or diesel multiple units (eg if you get a train from London to Cambridge that takes 45 minutes, that's an EMU). According to some random report i found on wikipedia [1], in 2011 there were 1248 locomotive-hauled carriages, 2892 DMU carriages, and 8046 EMU carriages. I could tell you a great many more particulars but suppose that you are tired of it by this time.
Loco hauled are very rare - HSTs from the 70s mainly being replaced on GWR mainline, a little use on WCML and cross country 2 or 3 sets?) and I think the east coast does them too. And Eurostar of course.
Aside from those it's freight and the sleepers isn't it?
If you're counting HSTs then everything on the east coast, plus great Eastern main line, the sleepers, East Midlands HSTs, Chilterns trains, 4 xc sets, the new transpennine sets that are being built, a few Cumbrian coast services, and within a few weeks the great western pocket rocket HSTs and the scotrail ones. Less popular than they used to be, but very rare is overstating it a bit
