I noticed something similar, but note OFCOM is allowing operators to use any part of their allocations for 4G services. I'm wondering if they're reusing some of their 2G and 3G bandwidth for 4G services.
Meanwhile, just about everybody who actually uses mobile networks seems to tell roughly the same story that I did before, and there seem to have been occasional more rigorous/scientific surveys that showed a definite, measurable drop in service quality on 2G and 3G over the relevant time period.