Just pulled 981mb down 298mb up over wifi to BT London test server.

Just as a point of comparison - 2degrees AKL I get 7.51 down and 39.77 to that Clouvider server.

Meanwhile, to BT London (same as toejam316 I assume) I get 235.66 down and 28.23 up.

https://www.speedtest.net/my-result/a/11714488064

360/30 to London BT on Quic, on a very old MacBook over Wi-Fi. I'm too lazy to get up and try the desktop :)

Clouvider, on the other hand, is sitting at 17/67.

High latency + even a tiny amount of packet loss is going to have a profound impact on throughoutput, it's just the way standard non-optimised TCP transmissions work. At shorter distances / lower latencies the issue is somewhat masked over as the cost of each retransmit is less.

As a matter of course, also check you're using the correct DNS settings for your provider, that can impact whether you get some context from the best CDN locations over a further one too.