I replaced 2 smoke alarms for a customer and asked 40 pounds, but she only agreed to pay me 30 pounds, i said ok because we did not agree with the price in advance, then she is asking for the invoice and 10 year warranty, and i did not keep the invoice and cannot find 10 year warranty in the box, so finally she only happy to pay me 10 pounds, i am very unhappy and decide to go to court, althoug we do not have contract but i keep all the correspondence in emails, do you guys think i can win? cheers