The 4G at Glastonbury was really really poor. Speed test app on my iPhone 6 would fail to find the best server at the worst times. Most of the time speeds were 0.5megabit/s-2.5megabit/s. Highest I got around 14megabit/s and that was early on Wednesday morning.
Call dropping/call establish failure was awful too, especially around the main areas (pyramid mostly). Lost signal a few times there too.
Barely any signal in Shangri-la either, 1 bar of 3G at best. Didn't see 4G at anytime in Shangri-La.