Ok so managed to eliminate all the additional latency by now running an ethernet cable to a switch and then on to my devices, quite a neat little job with some slimline trunking as well. I've capped the downstream speed to 40 Mbps in an attempt to force interleaving to be removed, no ES errors since I switched to the HG612 let alone capping the speed so maybe a suspect ISP modem/router causing issues? See what happens over the next few days and hopefully if it's removed I can remove the cap. If the errors creep up however I'll look closer at the internal wiring etc etc.
16ms may not be a lot in the grand scheme of things but the software I use for work is extremely sensitive to it and it's very frustrating at best to have a slight delay compare with when the latency was less than 8ms a few weeks ago.
