@CuptoCup 

Could be the cable, that should be easy to check if you replace it by the different cable.

Also check if you do have Deco S4 and not Deco E4 by any chance. Deco E4 has 100Mbit Ethernet ports and will deliver about the speeds you do see. If you are not sure, attach wired device such as laptop, with gigabit Ethernet card, to second Ethernet port of Main Deco. If laptop negotiates Ethernet link of only 100Mbps, that is where the problem is.

See this FAQ, it may be helpful: Using QoS feature of Deco

Turn off 2.4GHz in Deco app, for Deco Main Network, and run speed tests again with just WiFi5:

  @Alexandre. 

Cable check turns out I used another anyway (Cat 5) so that's not the issue.

S4 packaging and S4 on underside of pods, so pretty sure they're S4's unless they have been rebranded!

Tried turning off 2.4, same results.

Always 60-70.

Checked internet connection speed, 433mbps.

QoS set at 400 up 400 down.

Running out of ideas, your help is much appreciated. 

 to add, having seen other similar posts this seems to be a regular problem with Deco S4s only managing 60-70 mbps with Virgin hub in modem mode.

This negates the original reason for purchasing the Decos as I live in an old house and needed the extra reach of the mesh.

The network seems to work just fine with good signal all over, it just never gets the speeds that I pay Virgin for.

There must be a specific problem if every time I speed check I get the exact same results (60-70).

  @CuptoCup 

The only other thing left to try is rollback Hub to gateway mode, and configure Deco mesh to run in Access Point mode. How to set up Deco to work in Access Point mode

Then, try running speed tests again, with 2.4GHz turned off.

If that does not help, then it makes sense to return Deco and try WiFi mesh from the different brand.

CuptoCup wrote

thanks for the advice, i'll try in AP later. Any reason why deco app would say bandwidth 50m?

  @CuptoCup 

I have no idea. I tried it, with my Deco running in AP mode, it told me I am offline. Which I am definitely not.