Ah sorry -- I am getting all confuddled here and mixing Faith and FSS ---- so ....
You went to Faith, who passed you to Vanguard. But also went to FSS whose proposal you have signed --- yes ?
I would be inclined to leave it as it is after checking if Vanguard will charge or not. That said FSS do say on their website: "There are no upfront costs and payments will only commence on approval of your IVA. If your IVA is not successful you will not be charged."
You really need to sit down with a cuppa and breathe before deciding what to do.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014 http://foggy.blogs.iva.co.uk