I have just found your thread Dotcom and am saddened and disgusted by your story as you seem to be making every effort to cooperate with these vile people! I'm in a very similar situation to you, the difference being that Acenden have started repossession proceedings and I am fighting them.
What I have learned from reading similar stories about SPML/Capstone/Acenden is that the loan is designed to set the borrower up to fail, allowing the lender to ultimately repossess your home. I suspect that yours is a classic case of mis-selling, as is mine.
You can expect the FOS to take quite a while to review your case, and in the meantime Acenden MAY move to litigation in which case you would come across a whole raft of new fees!!
The only thing I can suggest at this point is to write to Acenden again informing them that should they move to litigation then you will immediately request a suspended possession order as the FOS are investigating a complaint made to them regarding your account. You could also review the criteria for mis-selling and make an additional complaint to the FOS if you feel that the loan was mis-sold. Add this information to your letter to Acenden, should you decide to start a complaint for mis-selling.
P x x