I have been having issues everytime i'm in busy parts of Central London, i have found dropping to 3G sometimes helps but sometimes this still doesn't work and no webpages will load or apps will respond, i had to find wi-fi.
This has happened once or twice in Central Birmingham as well around New Street this week, other areas are fine.
I'm using my One Plus 3T (whcih I've had for 18 months). Today I lost network coverage earlier today and it won't come back. I have turned off the phone multiple times, turned off mobile data, wifi everything but still have "Emergency calls only"
City of London, EC2N 1HQ, no download speed for data at all in the square mile. Been like it for over a month. Given up speaking to Customer Services who can’t seem to understand the issue or know of any course of action to rectify. Complete shambles and not fit for service mobile network. Should have the license pulled.
OK here are the results of some speedtests which illustrate the problem.
30th Dec - Carnaby Street London W1F - Download 0.4 Mbps 30th Dec - Walthamstow Central London E17 (46 minutes later) - Download 13.6 Mbps
I also ran some tests during yesterday at Fenchurch Street London EC3M (same phone at same spot on desk every time). You can see how the download speeds deteriorate from a respectable speed in the morning to unusable later in the day.
In all of the instances above, the phone was displaying 5 bars of signal and 4G - which gives a very strong indication that the service has been over sold, rather than a signal issue. It seems that there isn't the capacity to satisfy demand.