@Seyeclops 

I can think of two other ways how to update M9s with 1.2 firmware, and then I am out of ideas:

1. Promote M9 with 1.2 firmware back to Main Deco. Delete all three M9 with 1.6 firmware from Deco mesh. Your Deco mesh now consists of 1.2 firmware units only. Try Upgrade Assistant from Method 3, this is the simplest setup for it.

2. Delete Satellite M9 with firmware 1.2 from Deco mesh and try firmware recovery process on it to push newer firmware. See How to use firmware recovery if the Deco become brick

If that works, add it back to Deco mesh and do same with next M9 with 1.2 firmware.

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If you want to replace the whole M9 Plus Deco system with WiFi6 Deco set, I would recommend the following two options to choose from:

1. Tri-band Deco X90 or X95

or

2. More budget friendly but two-band Deco X55

You might not need six new Decos, especially if it is X90/X95. Start with set of three and add more only if necessary.

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If you have settings in your current Deco mesh you don't want to lose, the process of replacement should be the following:

1. Add new Deco (X55/90/95) as Satellite Deco to your Deco mesh;

2. Promote that new Deco to Main Deco;

3. Delete all M9 Plus from Deco mesh;

4. Add remaining new Deco units to your Deco mesh.

  @Seyeclops 

Sorry, one more replacement option to consider.

If you want new Deco units with same form factor as M9 Plus, especially if you need some of them wall mounted or ceiling mounted, consider Deco X50-POE. 

When I plan to replace my M9 Plus at some point, I'll go with X50-POE as I do need compact form factor and one of my Deco units is wall mounted in narrow corridor. Speed/performance/tri-band is less of concern for me, most of my Deco units are hardwired.

  @Alexandre. Thank you so much for your comprehensive and helpful responses. 
 

When I get time I will try to go through the steps to update the M9s.
 

Strange I can't connect to the older versions through an Ethernet cable. 
 

in the meantime I am going to move one of the updated versions into my office on the second floor so I have at least two floors covered (I need the main unit in the front room as that's where the Virgin router is - and need one in the back room as it is a very large extension in an old house and I have several WiFi intensive devices in there). 
 

have a good weekend. 
 

simon

  @Alexandre. 
 

so I have purchased 3 X95s as I could not update 3 of my 6 M9s. 
 

I intend to make one of the X95s the main Deco connected directly to my Virgin router, then use the other two around the house. Depending on how that works I could add updated M9s in the further recesses of the house. 
 

my question is about how to replace the M9s with the X95s. 
 

option 1 - remove all M9s from the system and then plug in main X95 and once up and running add the others OR

option 2 - add an X95 to the current system, then make it the main deco - remove the M9 main and plug the X95 into the router and then add others (as set above). 
 

I didn't want to remove the m9s and then plug the X95 in and find it doesn't connect as I will have to then reset the Virgin router to get it out of modern mode to connect to WiFi. 
 

your advice would be appreciated. 
 

cheers

simon

  @Seyeclops 

I would recommend Option 2. This document will explain how to promote X95 to Main Deco after you added it to Deco mesh as Satellite Deco: How to Set up the Satellite Deco or a new Deco to be the Main Deco

You can even speed the process by following "Case 2" from that document, which does not require adding X95 to Deco mesh as Satellite first. 

  @Alexandre. Brilliant - thanks. 
 

hopefully one final question. 
 

there is a 2.5ghz lan port on the x95 (as well as 2 x 1ghz) - am I best connecting my Virgin router to that or use it to connect to my switch which connects to IOT devices?

  @Alexandre. It is the new hub so yes it does. 

In that case, connect 2.5Gbps Ethernet port of Main Deco to 2.5Gbps Ethernet port of Virgin Hub.

  @Alexandre. Thanks very much. 
 

will get this all connected up tomorrow and hopefully improve connectivity around the house. 
 

your help is massively appreciated. 
 

simon