Self employed working for a sub contractor for a main contractor.Invoiced for kitchens fitted. I had the kitchens fitted signed off onsite by the main contractor which states that the kitchens fitted were to their specification and there were no issues when I left the plot. A week later and the company does have a cash flow problem, however they are saying they wont pay as there are problems with my work. I said that they were signed off by the main contractor as to their standard. Bear in mind other contracotrs go in once I leave sight and any other problems may have been cause by them.They said they were going to sight to look at the work. I said I would meet them there and walk through with them. They said no. I did any way and the only problem I could see was one mitre joint had opened (Mainly due to the contractor storing worktops in damp and they are damp when fitted - heating goes on and the may shrink. This I offered to fix immediately)Now they are not answering my calls.As I have the sign offs I feel I am entitled to payment and cant be held responsible for damage from other trades once I leave.Since this the company have been kicked off site by the main contractor.....Any advice?