Neighbours builders collapsed wall.

Our neighbours had an extension built, and the builders took down part of the supporting wall in our garden (on our property and without permission) in order to get a digger in when they were first pouring the foundations.

A few weeks later there was a giant crack going down the length of the wall and I mentioned it to the builder, who said that they would give us a quote for a repair and he would even do it for cost! 

A few days after that, the entire wall collapsed.

Now, a month or so later, the work is winding to an end, and we haven't heard anything from the builder again. We spoke to our neighbour about it and he brought it up with the builder who said he would get back to us. He is definitely avoiding us now--where he used to say hello and make small talk if we were coming in or in our garden he now acts like he can't see us at all. We expect him to not say or do anything about the wall, complete the job, and go.

So, what do we do now? We feel like while it wasn't a great wall to begin with, it was nowhere near collapsing until he pulled the end off, and it should be his responsibility to put it right. Are we right in thinking that? There is about a meter between their new extension and our house but we never had a party wall agreement--didn't even know we should have until I mentioned the wall situation to a friend.  We don't want to make a mess with our neighbours either. I am just frustrated and at a loss for what to do!

Not sure about all the legal ramifications....but I have taken to sending out letters over things like this. Nothing harsh - nice even, but just stating the situation and inquiring as to when a solution could be expected/further conversation is expected. Send it with a signature required thing and keep copies. Paper trail. Don't offer anything in the letter.

There is ascertainable damage to your property as a result of trespass (which is something illegal per se, even in the absence of damage). I would write a letter to the building company and the neighbours, stating the facts and with a demand to put things right at their own expense. If they refuse, sue them.

Some advice here:
http://www.adviceguide.org.uk/england/housing_e/housing_problems_where_you_live_e/neighbour_disputes.htm

Good luck getting it sorted.