We are, as debtors, really over a barrel in an IVA ! There is no mechanism for mediation or redress for us. All we really have, apart from the courts ( and the expense) is the IP's regulatory body -- who will, if they find in our favour, give the IP a slap on the wrists and, maybe, a fine ( sometimes eye wateringly large) --- but we get no recompense or resolution from the process. I have, twice, raised petitions on the subject but had very little support each time. Those in an IVA do not wish to rock the boat, those outside of the system are simply not interested (though, one day, they may find themselves joining our ranks !! ).
If you do not withdraw the complaint, or they do not come up with a satisfactory solution, you can pass the matter to their regulatory body here: https://www.gov.uk/complain-about-insol ... actitioner
I would only withdraw once they have satisfactorily addressed each part of your complaint. Remember, though, that they can only act within the insolvency rules and the terms in the IVA. The first thing I would want to know is how they arrived at the £85 payment they used in their advice -- and why they arrived at £217 at the creditors meeting -- somone, somewhere in their team was no good at maths ! Depending on the outcome of this a review might be required.
I would also get them to agree, in writing, that 3rd party access to your bank account is not required or authorised by you and they will ask for and accept hard copy statements and payslips, just like the majority of the industry.