crypticc you have been experiencing overutilisation since 2011? and nothings been done? bloody hell I am guessing there is no decent alternative provider in your area? I would of walked a long time ago.
I'm honestly sorry for your reduced speeds during the evenings. We do intend to increase capacity with a pending network upgrade. At the moment we're waiting for the pre-upgrade work to complete and that is due for review on 29/03/2017.
At that time we should have a better idea of when the actual upgrade work will commence.
You are entitled to a monthly credit whilst waiting so I'll pass your details on to another team who will be in touch to provide some advice - hopefully within a few days, though may be a little longer due to the festive period.