To see what speeds VM re supplying to your Hub you need to check on an ethernet cable connection first - if they are full speed then you can focus on why the wifi speeds are low - do the below.
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If you expect >100Mbps then.... Connect a 1GB enabled computer/laptop (check network card is set to 1GB) , with up to date drivers, via a NEW and working Cat5e/6a ethernet cable, directly to the Hub which you have put into “modem mode” (https://www.virginmedia.com/help/virgin-media-hub-modem-mode ).
Or go into the Hub settings and turn off/disable the wifi and also disconnect all ethernet cables from the Hub, except your one device. This ensures that NO other devices are connected
Test speeds at https://speedtest.samknows.com/ - or https://www.speedtest.net/ - try on 2 different browsers - as Chrome sometimes gives odd results.
If they are still low – boot your device into Windows safe+networking mode - to disable any potentially interfering software - and try again.
There are many posts on here (I have a list of ~30!) where QoS software, anti-virus, unknown/flaky software, old network card drivers, corrupted browsers, bad cables or other connected devices are limiting speeds on tests.
Report back what that gets.
For examples of why... see message 7 in the first thread and 9 in in the second and 3 in the third
https://community.virginmedia.com/t5/Speed/HUB-5-and-IGB-wifi/td-p/5088163
https://community.virginmedia.com/t5/Networking-and-WiFi/Slow-Ethernet-Speed/m-p/5060946#M484321
https://community.virginmedia.com/t5/Speed/Upgrade-from-M600-to-Gig1-no-speed-change-with-Hub-4/td-p/5065927
