[edit] Jesus, another long post, LOL.
Answer, your provider couldn't give a shit. There was a backlog/streetworks/morons in the way. Most likely your provider bought up some DSL cards for the exchange on the cheap: to find that only DSL2-DSLAM cards/systems can handle 8-24+meg anyway. DSL goes up to 6meg at a push.
Whatever, your upload and download speeds are dictated by a finger press at the exchange, depending on what you have signed-up for. Don't have the link anymore, but look into DSLAM on the net. Very clever
and small.
Sounds like BS doesn't it. Its not. Telephone lines are telephone lines and if your phone works - so should DSL. DSL2+ is even more robust that plain DSL. The only fact that remains true - is that distance to exchange (or Thames Water) will affect speed.
I had exactly the same 'speed' problem (2meg went to 1meg). A phonecall to service, a five minute (on the phone) test of line and an IP test- everything confirmed as normal. Nothing happened at my end.
Day after ...... Oh, lookey here - its 2meg.
I can confirm that it was as simple as them not bothering to re-assign my new tariff speed. How do I know? Its Germany. Make a complaint before 16:00hrs and usually its back the day after with German early-bird efficiency. Let's just say, it was 2meg by the time I woke up.
For two months I thought I was on the new tariff. Only found out when I started messing with the router software. Doh!
OT ... Deutsche Telekom have been installing these highly complex connection boxes on the street recently. These are so techno they have powered ventilation
Quite funny walking past one of these groaning things on a sunny day.
I reckon the Gerries are installing the new generation IP infrastructure - ahead of BT (who have said they are doing it) ;-)
P.S. Your router should report your subscribed up/down speeds.