OK, so it's nothing to do with WiFi at all. Let's forget about that.
There are a number of things you can do to check what's happening.
To start with, check that there is no local network issue by calling 0800 561 0061.
Set up a free BQM that will check your connection for dropouts, https://www.thinkbroadband.com/broadband/monitoring/quality and post on here the Live Link that is generated.
Go into your Hub on 192.168.0.1. Click on Check Router Status. Copy as text and post on here the Downstream Upstream and Network Log data