What happens to the charges?

I am very interested to know what happens to the illegal charges that were imposed on accounts by HSBC (HFC) when the debts were assigned to factoring companies such as Arrow Global, Phoenix Recoveries and Link Financial. Presumably the whole debt including the charge (which is added at the outset, before any solicitor action) is sold to the company, which will then attempt to collect the whole amount. I am currently investigating this area as I believe there are a huge amount of “collection charges” that could be reclaimed from the bank that have simply been hidden away in the assignment.

I am also interested to know if the solicitors involved in this practice who act for the factoring companies to enforce the debts also add charges upfront for their services.