I've been with Nildram (now Talk Talk business) for the good part of 5 years and have never had any real problems with them until a few months ago. I live close to our exchange, which serves a very small community, and so have always received 8mbit speeds at all times of the day.
The problem started very suddenly a few months ago. On some days, between approximately 5pm and 11pm each individual connection is limited to between 100KB/s and 200KB/s. That means if I run a speed test, my result is between 1 and 2 mbit. However, if I start 4-6 simultaneous downloads, I can achieve 8mbit speeds.
As you can imagine, this is quite annoying for services such as the iPlayer that use one single connection.
The problem seems very random. Some days it happens, some days it doesn't. Some days each connection is limited to a seemingly very precise 200KB/s, some days 100KB/s, some days less.
I have tried nearly every solution on my side I can think of, even replacing my router twice at 100 quid a pop each time. I've disconnected all the other devices from the router, turned the wifi off, ran tests from different computers, with no luck.
In the past I was sometimes able to 'fix' the problem by disconnecting and then connecting again from the router. This was touch and go though, and no longer seems to work. Even when it did 'fix' the problem, it started happening again after a couple of days.
In my correspondence so far with Talk Talk I have had one person agree that it seemed strange, but he seemed reluctant to say it was a problem on their side. Further replies from different support representatives have failed to understand the problem and have been the boilerplate "It's normal for speeds to decrease in the evening", despite the fact I can achieve 8mbit speeds with multiple downloads.
I'm really stuck here, and would appreciate advice as to what to try next.