My neighbour is refusing to pay

I do believe that unless you have something/anything in writing/text/Facebook etc, of some form of conversation of agreement between you and your neighbour to split the agreed/set price which you have Both Agreed too with the builder/contractor prior to the works/job commencing, then you yourself are unfortunately liable to pay the agreed price with the agreed contractor/builder. Once you have paid the contractor/builder and if you believe you have sufficient evidence of an agreement, you can then go to the (small claims?) court. I would speak with a solicitor if I was you just to be sure. All the best.

court

A complicated situation so let's clarify a few points first. A good trades-person will willingly provide a written quote for your records as well as receipts or invoices too, failure to do this only highlights their lack of process and therefore being unprofessional despite quality of work, avoid at all costs. Besides these facts, the agreement, verbal as it is does bind you and the trades-person could pursue you through court for it, be prepared for that course of action if payment is withheld. The agreement between yourself and neighbour, endless to say, was highly unusual and is not expected by a trades-person, its usually one resident or another, never both. With those facts in place, you are solely responsible for the cost as the agreement was between you and the trades-person. Unfortunately despite many assumptions, there is no law governing property borders, only what is included in property specific "Conveyance Deeds", see here: http://www.boundary-problems.co.uk/boundary-problems/fences.html I hope for all concerned, to avoid escalating costs, you choose to pay, as if you do not, you may be bound, and be forced to pay regardless.

Whoever asked for the quote and excepted the quote is responsible for the bill, The decision between the two neighbours is a separate matter and needs to besorted between them either amicably or through the courts provided their is written proof that is showing they will split the bill