I have a client who has had communications from Council Tax office to advise that they will be arresting his bank account due to non payment. Since this he has moved all benefit payments he receives to a Post Office account however we are unsure of they can also arrest this account or if it only applies to the bank account.

I think this only applies to bank/building society accounts (but don't quote me).

I also think that SS and HMRC benefits (if they can be identified by the bank) are exempt from arresstment.

Any further benefits paid into the arrested account after the arrestement has been served on the bank are also exempt from arrestment.

You really should read the following:

http://www.consumeractiongroup.co.uk/forum/general-debt-issues/87560-bank-account-arrestment.html