Had a chat with someone about my connection, they ran the usual tests on my line and said there was no problems, which obviously isn't really the case, there's just no issue as far they can tell from the limited testing done. I know there's no issue on my side, all ethernet cables are cat6 or above, Intel nic is 1Gbp capable and is updated with the latest drivers and configured correctly. My home LAN works perfectly well.
After some more digging I used Ping Plotter to take a look at the route my connection takes to some servers, this is what I found:
As you can see there is one particular hop that is all over the place, (126.96.36.199 / 50-14-250-212.static.virginm.net) After watching this for some time you can see the latency jumps up momentarily from the normal average of around 15-16ms to anything between 80ms and 3000ms, you can also see almost 20% packet loss at that location. There is obviously something wrong with this server/hop. Location: https://www.speedguide.net/ip/188.8.131.52
It would be nice if the Virgin forum guys could somehow get the engineers/technicians to look into the issues with this server, since sending an engineer out to me is probably going to be pointless if my traffic keeps getting routed through the dodgy server.
Quick update on my issues. The engineer came today and swapped out a couple of splitters, inside and outside, which improved the situation a bit, he still wasn't completely happy though so he went to the cabinet I'm connected to which is pretty much right outside, across the road. He swapped out a few bits and pieces in the cabinet that he said were looking a bit worse for wear and jigged around in there for about 15mins, because it was "A bit of a mess in there." When we checked my connection again everything appears to be much better. Jitter is anywhere between 0 and 9ms, latency is much more stable again with just the occasional small spike and RTT is back where you'd expect it to be for UK servers.
The Ping Plotter screenshot I uploaded above shows the 8 hops to the www.akamai.com server, it now only takes 6 hops to reach it and there is no longer a huge spike in latency on one of the hops. Power levels are also better, around 46-47 on the upstream and around 6-7 for downstream, would have liked the downstream a little lower, but, you can't have it all I guess. Bufferbloat hasn't really changed that much, although there was slight improvement there, I've come to expect some bloat due to the Puma 6 issue and I've always managed to keep that mostly under control for gaming with the Edgerouter X and fq_codel.
All in all, very happy so far. Thanks to those who helped out, especially Alex_RM and the engineer (didn't catch his name,) tonight will be the acid test though, I'll play some BFV, since that game suffered the worst, and will report back tomorrow with a final update.
Sorry for the late reply. So far so good, jitter/latency does get a bit worse around peak times, but it's manageable. The main thing is that the large spikes have been reduced considerably, still not as good as it once was, sadly, but I can enable QoS on the Edgerouter X when gaming and that reduces the Bufferbloat and smooths things out considerably. Oddly enough though the long RTT reported by DSLReports are back again, when I run their test with no QoS it reports 100ms+ to servers here in the UK, enable QoS and it comes right down to sub 30ms? Strange.
I have what looks like a similar problem with BFV on PS4 and Xbox one S with SH2ac and an Apple Extreme 6G router. Posted about this today. Been like you with VM for around 15-20 years and getting fed up with sudden ping spikes in game, when friend with BT and only 60mb max is on 15-20 ping to my best 20-30 ping.
Really hope my issue can be sorted better otherwise may have to do the un thinkable and leave VM. My house doesn't even have a BT cable to the house any more! LOL.