Fibre BB speed issue on Ethernet switch

1gig TPLink  ethernet switch connected to back of Sky router, which in turn is connected to a Sky router with 1gig Fibre to the prem .

Connected to the switch Skyq wifi booster  and mini box and a PC.

When I run a BB speed test the PC reports back around 200 meg. If I disconnect the sky equipment I get around 900 meg.

What is the Skyq equipment doing to cause such a slow down in Internet access speeds?

Are you doing all your speed tests using Ethernet cabling to the router?

If you're doing speed tests using both Ethernet (wired) and WiFi (wireless) there's often some discrepancy involved. Ethernet will tend to be more consistent, WiFi tends to be more variable. Networking packets travel consistently to and from (symmetrically) using a physical cable. With WiFi however, it's an exchange to or from (asymmetrically). WiFi is more prone to all kinds of signal interference -- channel issues, electrical noise from other appliances, and especially when extenders are involved, improper range distance issues.

On the other hand, if you are using just Ethernet cables between devices, that kind of 900 -- 200 difference is puzzling. How extensive is the setup/settings menu in your router? Are there any options regarding bandwidth regulation?

That might be a case to contact your ISP.