You can stop now, you have made the decision to go for an IVA, if you can build up a bit of money now, it will help towards anything that might happen duing the IVA, like the washing machine (heaven forbid) breaking or something.
The call centres that phone you up are paid to extract as much money as they can from you and will threaten all sorts of things. They are basically just doing their job. Some dont even know what an IVA is. It would cost the companies a fortune to do house calls, although it does happen, its really very rare. I didnt pay my creditors for 12 months and didnt get one, I was threatened though.
In my humble opinion its not worth entering into a converstation with these people, they are NOT interested, dont care, and rarely listen anyway. They want money and thats all. So just tell them your intentions and hang up. Dont be bullied, you dont have to go hungry because Lloyds TSB think you should.