Dodgy suppliers!

Hi All

I'm in the process of finishing up a rear extension. All has gone well up to the point of getting the worksurfaces put in. I found a company via ebay who supply and fit. I've used guys off ebay before and have been pretty happy. They came and measured up but brought the wrong sample. However, I knew which one i wanted and they quoted on that basis. Having received the quote i agreed to pay 30% upfront (i was a bit nervous about this as they weren't a known group). On the day they were supposed to install i got a phonecall telling me that they'd cut the wrong type of worksurface but they would remedy this and install possibly later in the week. I was told i'd get a call that evening. Heard nothing, sent texts and left voicemails with no reply. I'd go via their sales team who were pleasant but not very helpful as the boss was the main guy who messed up. I have been getting more and more frustrated as the process has dragged on. I asked for a refund but was told that the job was half done and they were waiting onone more slab to complete. However, they then offered to supply a different design so what difference does it make. I've been getting more threatening (in a nice way) but i'm getting litle info from them.
Any idea where i can go? I just want my money back now