who can i complain to about the way CAPQUEST DEBT RECOVERY are bullying me and pressuring me? read on pls....?

i originally had a credit card from capital one bank, with a limit of £200. i had difficulties making payments back to capital one bank, and my balance rockted up to around £558 because of late charges/interest added onto my account. my debt was then passed over to CAPQUEST DEBT RECOVERY, and i was making regular payments of £40 each month to clear up my debt. over the last few months, i have had alot of difficulties paying any money to CAPQUEST, due to being made redundant, aswell as other big issues which are affecting my life in a big way.
i am currently homeless,and sleeping rough, and waiting for help to go into a detox/rehab,as i am suffering from drink/drug/health issues. i am currently claiming incapacity benefit/income support, as i am awaiting counselling from my GP,because the death of my brother, and am receiving regular medical certificates from my GP for depression. i am on medication, both anti depressants and sleeping tablets because of my issues i am dealing with at the moment.
due to not being able to keep up with the payments to CAPQUEST each month, i am getting phone calls to my mobile, bullying me and pressuring me into agreeing to pay a certain amount each month. im a very vulnerable person, because of insecurities in my life right now, and feel that telephone reprasentatives from CAPQUEST and treating and talking to me unfairly. over the last year,i have managed to get the debt brought down from £558, to £220,over the last year or so.(the original debt was 200). i have always corresponded to capquest, and kept them informed with my situation, so i havent been ignoring them.
i feel im being very unfairly treated, and dont kinow what to do. the most recent amount agreed to pay has been 10 each month, and when a payment is not paid,i am having even more interest/charges thrown onto my account? what are my rights?? who can i contact? someone please help, as i dont know where to turn.
my last call from CAPQUEST, was on friday 19 september, and was told my account will now be passed over to a bailiff/debt collector. i am no longer at the original address where i was living when i got the credit card from CAPITAL ONE BANK, as i am homeless and sleeping rough, but have always contacted them in writing, stating that my previous address, is no longer where i live, but simply a correspondence address to receive letters from capquest.
..im desperate...thanks for reading this people

: http://alcoholdrugstreatment.info/who-can-i-complain-to-about-the-way-capquest-debt-recovery-are-bullying-me-and-pressuring-me-read-on-pls