Hi cb and welcome to the forum
I have several clients with children in private education, so it can be allowable so long as it is justified. Creditors would be quite reluctant to be responsible for disturbing an innocent child's eductation, and there has been recent caselaw which makes this a legitimate expense under bankruptcy proceedings.
You will have to be prepared to consider equity release if you wish to propose an IVA.
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