Hi rosie
Do you really mean that your parents have one unsecured debt totalling £135k, or is this the total of a number of debts?
As your parents have equity in their property, which is more than the amount they owe, then an IVA will not be possible unless there are exceptional circumstances.
What I suggest they do is explore the cost of re-mortgaging the property - perhaps by taking an interest only loan for a while until they get back on their feet - and then using those monies to substantially reduce their debts.
With that sort of money (they ought to be able to borrow up to 95% of the property's value), they ought to be able to seek discounts on settlements, and perhaps reduce their balances to an affordable level if they do not clear them in full.
Hope this is useful, but post more if you want to.
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