@PeteFl Just to note also QOS set to 1000 up 1000 down

  @PeteFl 

If you have a Virgin media super hub (UK) running in its default router mode, I suggest for troubleshooting purposes to configure Deco mesh to run in Access Point mode. You can undo that change after you've done with troubleshooting, if you want to. Switching a Deco to Access Point (AP) Mode

In that mode, Deco mesh will not have any parameters restricting bandwidth.

If after that you are still getting 100Mbps on Ethernet from office unit, it means one of Ethernet links in your network runs at 100Mbps speeds. You will need to trace which one it is.

What is connected to office unit by Ethernet in the office, is it laptop or is it desktop? If I know that, and if it is device with gigabit Ethernet port that you can carry with you through the house, I can provide you with steps to definitely establish where is it you have 100Mbps instead of gigabit.

  @Alexandre. Hi Alex

I tried access point mode, still seeing same issue, I have also now replaced all cables with brand new cat6 leads. 

It is connected to a desktop pc sadly. 

Pete

  @PeteFl 

OK, so this is not Deco mesh settings. 

1. Check link speed on desktop PC: How to check the associated/link speed on a wired client

2. Do you have smartphone you can use for speed testing? It can help with tracing where the issue could be. 

3. Please provide exact model name of Netgear switch.

4. What app/web site do you use on PC for speed testing?