Really sorry you've not solved it.
The line and equipment remains a focus then. Regardless of anything else, the dreaded DLM may kick in and take a couple of weeks or more to bring the line back to its true potential.
Different ISP, but ...
... almost an exact same story.
Though, there's no option to select Annex B in my router. Just like this person: https://community.bt.com/t5/BT-Infinity-Fibre-broadband/TP-Link-Archer-VR900-VDSL-2-router-modem/td-...
Select A/L/M. shown working - https://community.bt.com/t5/Home-setup-Wi-Fi-network/TP-LINK-Archer-VR900-AC-1900-Wireless-Dual-Band...
Yes either Annex A or A/L/M works for me.
Unfortunately I haven't solved it, no. I'm not even sure if it's specific hops or something only relevant to certain servers. I don't know how I can diagnose it either.
Regardless: on wired ethernet
Is it even worth getting a BT engineer out? I feel like they'd take one look at it and say nope everything's fine on our end and charge me £130 for the priviledge.
Looks fine to me but maybe it shouldn't be varying by that much, not sure. Then again round trip is fine. I was pinging the closest pingable server to the game.
The physical link is all over and done with by hop 3. If hop 3 isn't jittery, then the connection isn't misbehaving; the PPPoA connection has done its thing and right now you're looking at a well-behaved 6.7ms.
This shifts the focus. If the jitter is still killing gaming then the jitter isn't under "no load" conditions, unlike this testing. You can verify this with a longer sample in ping plotter while you're actually running a typical gaming scenario. Feels like we're either looking at a) its fixed with the new router, b) it is intermittent or c) QoS issues for low latency gaming.
I'm running a dedicated firewall (Sophos UTM) instead of a consumer grade router. This gives me a known (best available) QoS implementation (fq_codel) with lots of configurability but it doesn't give me UPNP so some gaming is a right PITA to set up. If your longer sample shows up the problem in your first hops, then the answer may be to research best QoS for gaming.
Ping plotter shows no problem at all with your connecion.
100% PL at hop 2 is normal as the router is configured not to respond to pings.
FWIW why not set up a broadband quality meter HERE? It's free and will continuously monitor your connection.
For others reading this you cannot do it with a BT Hub.
I'm now getting 50% or so packet loss on hop 3 whilst running the game with ping plotter. Is that notable?
Thanks I'll look into QoS.