Yes there is packet loss but practically speaking isn't that just a ping that has not replied within a reasonable amount of time (4 seconds on Windows though I don't know what kit is running the BQM - Firebrick) and therefore just higher latency?
lost pings (packet loss) when the connection is being maxed out is expected, so the small amount of red is normal. The main question is why you're getting such significant amount of blue and yellow, given your green is stable. If you compare to mine (also on plusnet) you can see that when I'm just using web etc you get almost nothing on the graph, but when I upload/download (or stream video e.g. Netflix) then the latency increases as the connection is used.
As you've already tried turning everything off and its made no difference, it _could_ be that your particular router just returns pings in its own time. The only way to compare would be for someone else using the same router to post, or for you to try a different router.
Another test you could do is set up a third party ping test: F8lure has their own system and also a Firebrick but they are on different networks to Thinkbroadband's. Could be worth setting one up for a few days to see if you get any different data.
http://fruk.net/index.php?fruk=f8lure
plusnet unlimited fibre - 2 Jun 14 - 470m - 80/20 - Summer/dry sync 55/9.4, Winter/wet sync 52/9.1
15 years broadband (1999 ntl:cable trial) - Asus RT-AC68U with HG612 - BQM - Summer PN speed - Winter PN speed