I have some good news.

I raised an issue with my ISP. They've issued me with a new IP. I don't know what else they did but it has resolved the issue.

I have also raised an issue with redhat developers working on `openssh`.

They said this is a known issue especially in the VMWare community:

https://communities.vmware.com/thread/590825

The issue is related to a change in OpenSSH_7.8 relating to the `QoS` flag.

The **workaround** is to use the following in your `~/.ssh/config` file

    Host *
        IPQoS=throughput

I will not mark this as the answer until I can confirm it working on my end.