They have both added charges since I missed the payments. I have PPI on my Paypal credit card

Hi Ive gotten myself into a deep hole and don't know how to get out of it. In April last year I lost my job after having time off when my Mum died. Since then I have had no job. I am now on JSA and I have 3 credit cards and various bills. I have a Barclaycard which I am paying £50 per month but have missed most of the payments on my other 2 cards. One is a Captital one credit card and the other is a Paypal (Santander) credit card. About a year ago I used the last of my savings and took as much as possible from my paypal and capital one credit cards to pay Cartel £495 to clear my credit cards, What a mistake that was. Anyway... Ive now started receiving letter from Fairfax solicitors about my Paypal (Santander) card basically saying they want there money back, I've also received letters from another company about my Capital one card. What do I do?? TIA Paul