If you are a sole trader, you do not need a business bank account.
I went through a divorce a few years back, i know what it can be like its a nasty state of affairs to deal with.
I had some financial issues to contend with also, all i did was open a basic bank account with lloyds tsb, and started the business up again from scratch.
3 years on, and my finanical situation is pretty much a forgotten past, and the bank are now suggesting to me that i open a business account due to the ammount of money going through the account. I am resisting them as much as i can, until i have no option and they insist.
As long as you keep the account you are using for the business seperate from the account you use for personal expenses you shouldnt have any issues.
If your situation is so dire that you can only have one account, with no faciloties at all, then just cash only, and keep records to seperate your personal and business expenditure.
there is no legal requirement for a business account, the bank would prefer it as they can make money from you. If you have a ltd company, they you need a business account by law.