Just upgraded a week ago to the 200Mb broadband service and now getting only 100mb DL and poor wireless connections with lagg. Have carried out speed tests which confirm the drop in DL and ping latency over 30 ms?
Some devices do not have Gigabit ethernet adapters, so wired speeds will top out at just under 100Mbps. You will also need a Cat 5e (or better) Ethernet cable. Once you have determined you have equipment capable of 200Mbps, then you can try and diagnose any connection problems, starting with your power levels and logs.
Wireless reception is affected by many factors like Range, Client hardware, the Topograpy of your home, and the big killer, Wireless interference.
First of all, I would ensure the Hub is placed in a central, open position, away from obstacles and electrical devices.
You could try changing the wireless channel manually. Downloading a wireless scanner like InSSIDer for Windows or WiFiAnalyser for Android would help by showing you the surrounding wireless networks, the channels they are broadcasting on, and their signal strengths, so you can select the best wireless channel.
Setting the Hub's radio setting to 300Mbps (or 40Mhz channel) is not advised on the 2.4GHz band as it takes up over half of the available spectrum, making it prone to wireless interference..
I would also check for other sources of wireless interference such as A\V streaming devices, Baby monitors, Chordless phones, Microwave ovens, Plasma TVs, Security systems, etc.
Using the wider, usually less congested 5Ghz band could help, if your client devices support it.
If you care about wireless speeds get your own 3rd good AC router and upgrade your devices with AC network chips if they don't already have. Superhub wifi is basic and is there just to get you going as VM (and other ISPs) cannot and do not gaurentee wireless speeds as too many factors are outside their control.
~~~~~~~~~~~~~~~~~~~~~~~~~ All posts made are personal opinions as I do not work for VirginMedia. Kudo's a post if you find it useful and want to say thanks Mark a post as a helpful answer if it answers your question