I upgraded to 200mbs a couple of months ago, and at first I was getting around 190mbs, but recently I have barely been getting 110mbs. I use an ethernet cable and have run the speedtest multiple times, I have even tried resetting my router to see if that was the issue and it didn't fix anything.
Your Upstream is running a bit warm and needs to be looked at by VM.
It would be worth trying a different ethernet cable and temporarily disabling software firewall\antivirus software for testing purposes.
You will need to contact VM to look at your upstream, either by waiting here about a week until a VM Forum Team Member picks up the thread, or give them a call on 150 from a VM line or 0345 454 1111 for a quicker response.