I have successfully sued Tiscali, BE [O2] & UK Online for not providing the speeds promised. My basis was that as they provide - or other providers do but it is easy to get on the market - up to 2mbps products, it would be reasonable to expect that the service provided would be between 2mbps and 8mbps. As it never hit 2mbps in the space of a month - and they'd have to prove that
at your computer the download speed was above that, which would be virtually impossible - I was entitled to the difference in value between the service provided and the value of the service I had paid for.
I therefore claimed the difference plus
interest from the date of paying them. I am hitting Demon [Thus PLC] with my claim being filed and issued tomorrow. As they don't have a 2mbps service that was comparable [i.e. home], I found the another one on the net and charged them the difference between the cost of that one and the theirs.
Also, as their "service" had dropouts at frequent times and their indian customer "service" refused or couldn't help me, I used mobile internet as I couldn't stop using it for essential business needs, so I've charged them for those costs too.
Some useful tips for others maybe.