Plus the house I'm moving into is a new build therefore wiring should all be brand new. When you say, depends how the extension socket is wired. What do you mean by this?
In a new build, the builders usually fit extension sockets in every room, all daisy chained together. This will have a bad effect on the connection speed, so you may have to alter the wiring, or better still, fit a filtered master socket, and an RJ11 data extension cable to the home hub.
I would wait and see.
Do you know the IP or URL of your game server? Can you run a tracert to it from a command window?
I received my replacement router, however I still was having the same issues with disconnecting from online games. After doing various tests I came to the conclusion the issue was with my xbox one x. Therefore, I done a bit research into wifi issues with xbox one x and I found quite few people having a similiar problems to myself with their xbox one x. I have provided link to the forums covering this issue below
Here you will see that this is a common issue with the xbox one x, hopefully this is software issue rather than hardware.
Therefore, I have found a solution or work around until microsoft releases a fix, I have connected my xbox one x to a wifi extender specifically the BT 750 wifi range extender dual band, you can pick one up for £26. So at the moment my xbox is connected via ethernet to the wifi extender, therefore using the extender to receive the wifi signal. After 3 hour of playing online, I have not experience any disonnecting or lag were the game would freeze for second. The connection has been pretty good through the wifi extender so far.
I have also ran speed test and I'm happy to report the connectng via wifi extender resulted in no loss of connection speed or increase in latency/ping.
Another option you could consider are powerline adapters, however in my experience I have found them to be more of a miss than hit, because when connected I would get quite alot of variency my latency/ping and this can be just as bad as having a high ping/latency.
However they could workout for you.
Hope this helps.