If you ask your IP to call a variation meeting, this will involve him/her in doing additional work and it is fair that they be paid for this - although I am increasing seeing that creditors are reluctant to recognise this and expect us to do the work for nothing! The terms of your IVA proposal are likely to confirm that amount that would be charged for putting forward a variation, and who is responsible for paying the fee - be it the creditors or yourself.
If your variation is initially refused, you can negotiate to put forward a more favourable offer - but my advice is get it right the first time and there should be nothing to worry about. Your variation meeting should not, however, be put forward until you are certain as to the position at work.
Your windfall would not serve as a sweetener, as creditors are entitled to this in any case.
Hope this helps.
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