Welcome to the forum. I find it almost unbelievable that anybody purchasing defective goods doesn't return them to their supplier for a refund or replacement. And after purchasing previous defective goods or services fails to take preventive action to ensure it doesn't happen again. There are numerous laws and legal rights that consumers can use and implement to get refunds if they consider they have been mis sold a product. (also known as being ripped off). Of course some consumers fail to shop around, consider different suppliers, get multiple quotes for the product they are interested in. Or get written quotes and or agree incremental payment terms for larger purchases. Cheapest may not be the best, the saying "if it sounds to good to be true it probably is' very often applies to the cost cutting option. Most reputable tradesmen will be happy to provide a written contract agreement for some work and would look favorably at a reasonable stage payment plan. It is not that difficult to avoid been repeatedly ripped off providing you do a bit of research, shop around for at least three quotes and ask for references and recommendations from previous customers.
Doc H.