The router config is ok and as this slow speed is with LInux too software is ruled OUT
Went on virgin media's website on my phone and used the whatsapp chat function, after one and a half hours was told that we cannot help because I was chatting with virginmedia Ireland!
Could you access your router using http://192.168.0.1/ or http://192.168.100.1 for modem mode . You shouldn't need log in, select the 'Check Router Status' option and paste your 'Downstream', 'Upstream', and 'Network Log' tabs? Please copy/paste this data as text, split between multiple posts (Sometimes you have to click 'Post' twice due to an error message).
We can have a look for any oddities in the stats.
Could you please create a BQM (Broadband Quality Monitor) here, and post the live link?