Perfect, it looks like your packet loss happens on the connection between dsldevice.lan and 172.16.18.21.
Try these these two commands and let them do minimum 100 pings each:
ping dsldevice.lan -t -l 1000
ping 172.16.18.21 -t -l 1000
Do you know what these two intermediate devices are? Are they yours or part of your ISP’s infrastructure?
If you are to report to your ISP, then do a similar ping report to your own last device (typically your dsl modem) to prove your own network is OK. I guess this is the command (or maybe dsldevice.lan):
ping 10.0.0.1 -t -l 1000
and then a ping to the homepage of your provider (it will travel entirely in their own net). I guess this is the command:
ping www.bt.com -t -l 1000 # owner of www.plus.net
If it doesn’t respond at all, then try pinging a major local news site, e.g.:
ping bbc.co.uk -t -l 1000
This will (hopefully) prove that packets are lost while being handled by your ISP.
You may also be able to login into your dsl modem and find a diagnostic menu that will allow you to send a series of ping to your providers homepage. If you can prove packet loss from the dsl modem they provided to their own homepage, then your have extremely solid proof.