Upping prices and cutting data usage (by pushing AYCE up in price, and possibly eventually into history, having been replaced with a 8/10, 15, 20, 25 or 30 plan (or whatever) as the maximum, is one way to fix things though.
In fact, cutting usage could easily be seen as a cheaper solution than investing in loads of new capacity. Of course, once they add more 1800 sites, get more spectrum, switch on 800 etc then some of the current issues will be fixed to a degree, but only until they get more users and the problems start over.
Not even EE is immune to that, but it seems that for the most part, even in the busiest parts of London it is coping admirably well.