Hi jl and welcome to the forum
That depends upon how the property was to be treated within your IVA. Did you agree to have the property revalued during the fourth year, and then effect an equity release? If so, you will need to get your Supervisor's permission to sell, and this provision will therefore be transferred to the new property.
If the property was not included within the IVA, then you are free to do as you please, but obviously your new mortgage payments must not disturb your ability to fund your IVA payments.
Talk to your Supervisor for more specific advice.
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