Hi tramps, and welcome to the forums.
To my knowledge, there is only HSBC/First Direct who habitually close accounts when you are under an IVA. Other banks do not seem to mind you operating a basic current account (with no overdraft) whilst in an IVA.
As you correctly state, if you are with a bank who are one of your creditors, then you should open a new account with a different bank, as they can use any money in your current account to offset any monies you owe them.
Co-operative Bank and LloydsTSB are two that appear to be favourable at the moment, providing neither of them are your creditors.
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http://cr15py.blogs.iva.co.uk