CDS is only traded OTC atm, I trade CDS for a hedge fund so deal with the sales traders on different IB credit desks. I have no idea how you can PA trade it, not sure its possible. LCH Clearnet are trying to start a centralised clearing house but not all the banks have signed up so i thinks its still going to be a while until it is in place.
I would have through that there is a broker somewhere that can set you up an account with, its gonna cost you loads in margin and spread though. Alot of CDS trade upfront 5% and very risky companies have a margin of 95% upfront, the product is only for institutions really.
Also you would need QuoteVision to keep track of market prices and that cost £1,000 per month alone.