We are experiencing speed problems to many servers. Our broadband is BT Fibre. While accessing some sites is very fast, sometimes others are slow.

For example downloading from Bitbucket from the UK is peaking on 600kB/s, then after a minute, it's dropping to 60kB/s, then stays there for the following 15 minutes.

The same content downloaded from one of our servers in a UK data centre stays on 600kB/s.

I think this is a clear evidence that the service provider is cutting the bandwidth after a minute, which is not what we paid for.