Replacement Roofs

My next door neighbour terraced villa had to have a replacement roof due too leaks. That is when my troubles started. My roof started to leak from next door and because of the lock down it was nearly a year and a half before a roofer came to look at it By then my whole roof was wet and I decided to get a new roof as well. I did not tell my neighbour it was the fault of her roofers for doing a bad job. She is her 80 and suffers from strokes and is in and out of hospital After my job was done and I paid my roofers I noticed sun light coming into my side of my roof it was coming in between the space on my side of wall. I informed my roofers and they said it was next doors fault as they used less tiles than standard practice. They did not mention the sub standard work until after they had taking my old roof down and said there would be no problems and that my roof would be watertight and it was not a problem. Todate I have had no water coming in, but I was not happy with the small sunlight coming in through the green membrane. They are now saying that it was not in my original quote which is correct and that I would have pay the extra money if I was to get it done correctly which thought if I had to pay I would. The are not going to remove my tiles but lifted and refit all next doors tiles My neighbour would not allow this as when I mentioned I would have to this sorted my roof she was not very happy that a small amount of her tiles would have to lifted which I thought would happen. She ok it but said if there was any damage I would have pay. (If she only knew) What I am after is there any other way round this does not involve all her tiles HELP. Sorry it is so long winded, also she paid cash to her roofers and has no guarantee etc.,