Area 26 Lisburn user here....Same problem of late.
So I recently upgraded my VM package from the "Big Kahuna" with Vivid 150, to the more recent "Full House" package with Vivid 200 broadband.
The package upgrade was carried out on the 29th of June 2017, and a new Superhub 3.0 router & V6 Tivo box were installed alongside the existing older Samsung Tivo box.
Previously I was using a Superhub 2.0 and getting 150Mbps without any issue. As soon as the Superhub 3.0 was installed, this dropped to anywhere between 11Mbps and 30Mbps and has not improved since.
Strangely, when I was activating the Superhub 3.0, it initially synced at the 150Mbps, but after a few automated reboots, and I assume firmware updates... it only reaches a maximum of around 30Mbps.
A Virgin Media engineer was booked to investigate the broadband issue, and when he came out....he said that he could not do anything about the speed.
Numerous calls to broadband support have yielded no resolution, or even an explanation why the broadband speed has decreased so much. I just end up getting put on hold, and reset signals being sent to my equipment - Which also knocks off various subscriptions on my two Tivo boxes which have to be re-activated with an additional phone call to the TV team. This same thing has happened on 3 occasions now. Just no good.
What I just don't understand why it was syncing at 150Mbps to begin with, then dropped. This suggests to me that I was moved to a different Exchange/Fibre Cabinet? I am aware that the Superhub 3 uses DOCSIS 3.0 to cater for the 300Mbps speeds, but the sudden speed drop is very questionable. I don't believe there is over subscription in the area, as I did see the Superhub 3 at a steady 150Mbps before the activation updates, and I had 150Mbps on the Superhub 2 without ANY issues before this.
I do intend to pursue credit on my account for loss of service until this is resolved...If I had known these issues would arise...I wouldn't have upgraded for an additional 50Mbps.
I'm just fed up getting no where on the phone with support....maybe I can get some answers here?
Firstly, hit them in the pocket - ask customer retentions for a Deadlock Letter (explain to them that they have clearly demonstrated that they cannot help you), then, since they have not proactively offered you a bill discount, you need to complain to CISAS (https://www.cedr.com/cisas/). Include the length of time you've had this issue. CISAS = Communications and Internet Services Adjudication Scheme, a scheme that VM has signed up to.
Secondly, have a look at this forum and take note that the vast majority of issues are directly related to over subscription (too much demand for the service). This is a growing problem (check out the recent BBC Watchdog on iPlayer re VM). You then have to weigh up accepting the current situation (with agreed bill reduction) - which may last several years, or if you're lucky enough you could try for a competitor e.g. BT Infinity. It would also be good to give Watchdog an email since they commonly do a follow up.