Just a quick update for anyone reading this post now or in the future.
I rang USCIS and I was told they were sending me a new biometrics appointment, each time I rang I made a point of double checking with the level two officer that the letter had a) been sent out again and b) to the correct address. Each time I asked they assured me that it had, so I decided to wait until I received the new letter. However, after receiving an RFE that was sent sometime after this letter was supposed to have been sent out a separate officer told me no letter was ever generated!
So I followed the walk in advice and the very friendly staff sorted it all out for me. If anyone comes up against a similar issue with biometrics, I would advise you to not to wait for any letters and try and do a walk in.
And thanks for all your help everyone.
Nick,
Thanks for getting back to me.
We didnt get RFE'd for the joint sponsor, we got RFE'd for something else and there was a message at the end saying we should get a joint sponsor so we did but its proving complicated.
We're trying to get it using your suggestion. Fingers crossed.