Hi Hampstead and all, I'm a bit late to this thread!
No offence meant to MarkOnline, but this isn't correct. If the BBL was taken out in the name of the limited company, and the company has actually been struck off, then this debt is no longer enforceable. A strike off going through cannot be considered breach of any terms that forces a director to be personally liable, unless there is a personal guarantee agreement.... which there isn't with BBLs.
However Mark may be right in one way, and NatWest may no longer wish to do business with you personally due to what has happened with your company. It is not something I have ever come across but I suppose it is possible. If so, they cannot keep any positive funds held in your personal bank account to offset the BBL. They should offer to send them to another personal account in your name.
Directors can be held personally liable for wrongful trading or fraud, but this will usually come as a result of investigation triggered by a company entering into liquidation. There is no such investigation when a company is dissolved.
In short, if the company is now dissolved the BBLs is no longer enforceable, and has effectively been written off. If NatWest no longer wish to provide you with a personal bank account, they should offer to send any positive funds in your personal account to a different bank account in your name. I suggest you speak with NatWest asap to clarify their position, and come back to this thread once you have an explanation from them.