Paul - like the user name! very good. Welcome to the site BTW
Dizzie. I really think you need to collect all this evidence then approach DD and tell them the problems you have had with them. Give them the oppurtunity to make ammends, or compensate you for the inconvenience. We all know that DD have done some good work in the past, so do have the abililty to do it again. If this doesn't work, then take all your evidence to trading standards, and ask them about the prospect of a refund of your money, as DD have not carried out what they were paid to do.