[andygrif]

To be quite honest, I think you're possibly on a hiding to nothing. If the service is as bad as you claim, cancel your services in writing, giving 30 days notice, citing the reason for your cancellation and find a supplier which better meets your needs.

You're unlikely to find anything in their company's T&Cs that you can claim against, the best hope you have if you really wanted to engage in legal action would be to contact your local Trading Standards office, OFCOM and the DTI.

The only way to recover some of your expenditure would be to have documented actaul speeds available to you for the period you're referring to (so for example if you were paying £35 per month for 10mb and you were getting something like 2mb which is worth £25 per month) then you could issue a claim against them for the £10pm for each of the months - but this would be very difficult to prove.

There is usually a clause in your contract stating that they do not guarantee speeds and/or connection.