I'm using AnyConnect (ocserv backed) VPN, so it presents as TCP/443 and 'upgrades' to UDP/443. Or at least, in theory it's supposed to. I don't think it's actually upgrading to UDP/443 on EE 4G, but throughput speeds with or without the VPN have dropped to <3Mbps in Central London (or 35Mbps+ as soon as I go somewhere less dense) that day to day, I don't notice any impact from the VPN vs not-VPN anyway...
I'm also Central London for work, I typically get at least 30/20 in the office without VPN, and at times up to 50/30, a lot less than the 80/80 I used to get 3-4 years ago in the same spot. With WireGuard I get consistently between 0 and ~10 down. I ran some tests with the guys in WireGuard IRC which seemed to confirm that the issue is specifically EE limiting UDP whether by QoS or otherwise.
