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thanks all, you're too quick for me!
honestly, I can't remember him signing anything to say he'd received the money from me.. stupid, I know. I will did out the paperwork, but I really don't think I got anything signed.. lesson learned :o(
I intend dropping off another official letter to his business premises (a small, grotty looking shop, it's always closed) telling him what I want done and by when, and will pay someone else and take him to court if necessary.
I was just steaming mad about his lies. I may text they guy who replaced the pump to see if he thinks I owe money to the boss.