To achieve a minimum dividend of 25p in the £, based upon the charging scale I use in my practice, would require monthly payments of approximately £425 per month - but please don't use that as a guideline as other IP's may charge more or less, and at the end of the day if all you can afford is £400 you should not agree to pay either £425 or £490.
Your are absolutely correct to be considering interest rate rises, and must take all contingencies into account. Why not take a second opinion from another IP to see how the advice differs?
Regards, Melanie Giles, Insolvency Practitioner for over 20 years.
For further details contact me at
http://www.melaniegiles.com and view my IVA blog at:
http://melaniegiles.blogs.iva.co.uk