Speed dropping at random intervals

Hi. I'm on O2 LLU. Since about March my normally ~5Mbps connection will drop suddenly to <1Mbps. Sometimes this is after three days, sometimes after 10 days. I haven't yet worked out anything that triggers it. It happens even when I've got nothing but my router plugged into my test socket so I'm sure it's an external issue.

A reboot of my router will bring my speed back up again for another arbitrary length of time.

O2 have been pretty good. They can see noise spikes on my line that are presumably causing this, they've replaced all my equipment and, even though Openreach couldn't find a fault, they've switched my ports in the DSLAM and redid some of my line terminations between home and my exchange. Dropping my noise margins didn't help either.

I'm not sure what to try next TBH. O2 seem to be out of ideas so is it just a case of grinning and bearing it?

Thanks for any advice.

Post your router stats.