Hi mel and welcome to the forum
You have to include all your debts into an IVA. Your mortgage will be unaffected by an IVA, so you will need to continue to maintain the payments. You can move your mortgage to another provider if you wish, but any savings will be absorbed in increased IVA payments. An IVA ought to take about a month to put forward to your creditors, and you may have a modest amount of savings whilst in an IVA but only to cover things like car and house maintenance and other contingencies. You can offer an early settlement depending upon where the money would be coming from and the dividend you have offered to your creditors.
Hope this helps, but please post more information about your services if you require 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