On the (UK) credit card front, if you find your card provider is being uncooperative about their "Joint and Several Liability" (Section 75 of the Consumer Credit Act 1974) then it's amazing how a bit of legal action speeds up their pedestrian correspondence and prompts them toward a reasonable conclusion!
I found this "support pack" to be a very useful tutorial:
Trading Standards Division - Consumer Advice - County Court Support Pack
And I was pleasantly surprised to find that part of the process has gone electronic:
http://www.moneyclaim.gov.uk/