With regard to IPs charging open-ended time costs these can be challenged by reference to Statement of Insolvency Practice 9. Copies available at
http://www.r3.org.uk/uploaded_documents ... ersion.pdf
But the essential document is called Technical Bulletin No.65 issued by R3 in August 2004. The bulletin was issued following an important judgement by Registrar Baister which set out a list of 'guiding principles' (including value for money and proportionality) against which fees can be judged.
You can ask your IP to justify their fees - and fees charged on a time cost basis are the hardest to justify. Would you pay a decorator by the hour ? How slowly can you paint.
If there is nothing extraordinary about an IVA and with a 'going rate' of £1000pa (which itself sometimes seems hard to justify) for supervisor's fees then anything significantly over this sum could be challenged as being 'excessive and disproportionate' on applicatin to the court under s.263 of the Insolvency Act.
It would be important to take legal advice first but I would suggest that the more IPs fees deviate from the going rate the greater the prospect of success.
£2,500 pa, for example, would be harder to justify than £1,150pa! 150% over the 'going rate' compared with 15% would be more likely to justify the risk of going to court.
But remember that if the court considered that an IP had overcharged then the money would go back into the IVA trust account and creditors would benefit (unless you've repaid everything owed) so it would make sense to get them on side from the start.
There would nonetheless be the satisfaction of knowing that you've repaid your creditors as you originally intended rather than lining the pockets of a profiteering IP.
If you won, the court judgement would also go against the IP with their professional body and it would also set precedent that should help other debtors.