Disregarding the upgrade and price for the time being (we can return to that) - can we look at what you are getting and why its low.
Firstly... Are the issues only evident on wifi connections or do you see them at the same times on devices connected on ethernet cables? If you don't know, can you check to help diagnose whether it is just a wifi issue or it could be network connection related?
What Hub model is it and what are the various Hub lights showing/doing when this happens?
And also make sure that the device is capable of receiving higher speeds - NIC card set to 1GB (not 100) and the ethernet cable is new and at least Cat5e (not Cat5 or earlier).
Then if speeds are still low can you test it as below to establish just what speed is coming to the Hub. ________________________________
As you expect >100Mbps then connect a 1GB enabled computer/laptop, 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 ). This ensures that NO other devices are connected
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, 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.
-------------------- John --------------------
I do not work for VM. My services: HD TV on VIP (+ Sky Sports & Movies & BT sport), x3 V6 boxes (1 wired 2 WiFi,) SH2 in modem mode with Airport Extreme Router +2 Airport Express's. On VIVID200, Talk Anytime Phone, x2 Mobile SIM only iPhones.