I've been told by Citizen's Advice before that if they don't want to talk to you, the best is to send a physical letter to their registered place of business with a clause such as "You have 7 business days to respond" etc. This then firmly places a time limit on how much stalling they can do.
Thats assuming Citizens Advice will even help you. My local Citizens Advice wouldnt help me, but thats headed up by a retired copper.
Edit: I've always found his ability to track me down in the middle of some woods when I was out walking to be a rather curious use of technology considering he was retired and wouldnt have access to mobile phone triangulation facilities or the gps facilities on my phone. However he outed himself when he went back to get some answers for me!
