My ISP said they can't change the routing (could be just an excuse), but did mention the packet loss may be due to DDOS protection where packets are dropped when too much data/requests is going through at once.

Might explain why this has only happened recently with no prior problems.

Just to add once again problem nodes - Cogentco:
te0-2-0-5.ccr21.lon01.atlas.cogentco.com [130.117.14.205]
be2314.ccr21.lon13.atlas.cogentco.com [154.54.72.253]
be2283.ccr21.lpl01.atlas.cogentco.com [130.117.49.34]

Frequent lag/lag spikes starts at peak time EU (after 9pm) and lasts for 2-3 hours.