Why did they increase your payments after 6 months? If the IVA has become unmanageable, and the IP will not reduce the payments, you could either pay a lower amount which you feel you could afford and see if they are prepared to default you for that purpose, or simply end the IVA. As you have an ability to fund a reasonable contribution, you could also consider a DMP which would give creditors a good return and enable you to set the level of monthly payment rather than your IP.
When you do go on ops, you could then always increase the payments from your tax free element. Just a thought - and as your IP firm have recently started posting on this forum, they may also be able to assist you directly.
Regards, Melanie Giles, Insolvency Practitioner