I had an ongoing problem with LM over my connection speed..supposed to be 512 up and 256 down..in reality 90-150 down and 650 up
LM ignored all correspondence, emails etc so I paid a solicitor to get involved.
LM deny any liability to provide any guaranteed level of service beyond their own idea of 'satisfactory.'
However since getting all the A* holes stirred up my speed is never less than 512K down and 300 up, usually around 750/450. Its now very good compared to what it was.
It pays to complain, and if that don't work start roaring and screaming and go to law..then you force them to take notice.