A F&F offer is based on the amount left to pay if the IVA ran it's course. So, assuming you rent and the IVA is for 60 months, you have 36 months left, or thereabouts, at £410.The creditors are therefore looking at around £14,760. This can be rounded down a little to represent admin savings, so maybe an offer in the region of £12k would be looked at favourably. I have seen lower offers accepted, but also higher ones rejected.
You have to make the offer to your IP, stating these are third party funds and only available for the purposes of a F&F -- should the offer be refused they will be retained by the donor. The IP will want to see evidence of the funds and source (father's bank statement) for money laundering regulation purposes.
Some people also stipulate that any payments made after a certain date, say 2 months after you make the offer, will be deducted from the lump sum.
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