My name is Alex Hughes and I'm happy to help with your question today. I need to ask you some preliminary questions to be able to help you.
Did you builder give an estimate of how much it would cost to repair/make good the damage?
It appears your neighbour has failed to comply with the Party Wall etc Act 1996 which governs the steps your neighbour should have taken before erecting the porch. Failure to comply with the Party Wall Act means that you could take your neighbourto court and obtain an injunction to remove the porch. Also your neighbour may be liable for causing loss and damage as a result of thr works. You should write to your neighbour to explain the legal position and that you are considering legal action. This may persuade your neighbour to engage with you in discussing a solution.