Hi Chris
Sorry you're having this problem. Unfortunately, it happened to us too and has been a constant form of annoyance and upset over the past few months! Like Ninasmum, i do hope it is just because they are busy. It's sad when a previously good relationship breaks down. I'll try and summarise how things have gone, with us being in a similar situation.
We were very naive when we got Bingley

in hindsight I would have been a lot less trusting and a lot more cautious. His breeder was recommended by some people who know, they never had any problems with them and everything had been perfect. When we first went to see him we were asked for suggestions for his full KC name after their affix, which we provided. When we went to pick him up we were told our suggestions had already been used, so they had to reapply using different names, so there was a delay in taking home the papers. We were told they would forward them onto us as soon as they arrived (this is actually even noted on our contract with them). Our relationship initially was great. I phoned the breeder about 3 times in the space of his first week at home with little niggles and questions, and she was happy to provide help and advice. We sent her emails, texts and pictures of him as he grew over the coming weeks. A couple of times we asked about progress with his registration and were promised it was all in the pipeline. Then, about four months ago they stopped responding to any contact from us. The KC are powerless in the situation, and we took advice from trading standards and my sister who is a solicitor. We've sent registered letters from us, my sister sent a letter as our solicitor. No response. We are very saddened that it has all come to this after such recommendations and a great start to our relationship. I get upset about it quite often, I hate feeling like I've been taken for a fool. I have learnt my lesson, and would never, ever, take a pup without papers again. Would I change Bingley? Not in a heartbeat. Sorry for the rant,

it's an incredibly frustrating situation to find yourself in.
Where you go from here depends on how far you wish to pursue the issue. It is very difficult, and frankly, I doubt very much that we will get anywhere with our chase. Do keep trying to contact them, and make sure you keep a record of all these attempts should you wish to pursue it further.
I really really hope that there is a genuine reason for this, and everything works well.