Hi I am having similar issues with slow broadband speed and continual dropouts for a long time and I'm on 100MB service and my speeds have been dropping down to 2.29Mbps download and 0.29Mbps Upload speeds regularly. Recently the speeds have improved but because I have a noisy cable to the house the signal still keeps dropping.
Eventually one of their engineers came out and tested my network which was fine and tested the outside line and said it has an unacceptably large amount of interference (electrical interference I presume or bad connections) on the line which is what causes the drop outs. He recommended a new cable from the box in the street to my house.
We have had this issue for 9+ months now. Every time we report it, there's a signal to noise fault which takes them 5-7 days to 'fix'. and I say it like that because the next day it'll be down again.
Just spent 2 hours on the phone raising a complaint but again it's a signal to noise vault. We literally have 0.00 upload speed today. It seems all that the network engineer does is swap a cable or something to the next port until another unlucky customer calls up.
We can't even browse the internet today using our M350 services.
It's a real shame because Virgin is the only company offering these speeds in the UK and 200mb+ isn't actually that fast, it is completely normal and commonplace in the US and Europe. Britain feels more and more like a steam-punk dystopia and when you have computers running off victorian infrastructure even more so
The engineer told me it is interference on the like caused by the old degrading cable. Think of it as the equivalent of the noise you get when you are between stations on an AM or FM radio but in a broadband context. And this affects/interferes with the ability to get a clean broadband signal to and from the router.