Hi Livingix, thanks for getting in touch.
As advised by apcyberax testing the speeds needs to be done via a wired connection for reliable results.
If the problems you're having seem to lie with WiFi specifically - it's performance can vary due to many factors beyond our control. If the WiFi troubleshooting tips here (virg.in/wifihelp) & here (virg.in/WiFiwins) don't help please try our Connect app (available for iOS & Android) for step-by-step WiFi diagnostics via the Broadband tab & keep us posted with how you get on.
Tom