Dispute with roof seal company

I signed up to a deal offered on the doorstep on the basis that my next door neighbour was happy with the work done for him. I was offered roof cleaning, roof seal, pipe painting, cleaning of paths, painting around bottom of house and round door and window frames, all for a bargain price. On day one of the 'work', I was at work, but neighbours witnessed workers on roof, cleaning it with a 'jetwash'. I got a phone call asking if the job was complete within a day or two of this, and had to complain that a number of roof tiles had been knocked out. They came back and sorted those tiles within a day, and then I heard nothing else from them. In the following month, both my husband and I tried to get a hold of the company to ask about the rest of the work, and we could not get any answers or responses to messages. I have received a couple of texts and phone calls offering appts to complete the work, and I have been stood up every time. This has been going on for 7 months now. I have just received a text this morning telling me that they have completed the work, and they now want to come and do 'the extras'. Surely I can refuse this work now, and refuse to pay?