Here is the financial ombudsman on a related question. My suspicion is that this stuff is all a bit untested but if I was the feminist group I would complain.
is a firm entitled to close a customer’s account – even without the customer’s agreement-
The general answer is – yes, the firm is entitled to do this. Like most other commercial organisations, banks and building societies are under no obligation to continue doing business with someone if they do not consider it appropriate to do so. But they should not decide to close an account for an improper reason – for instance, because of unfair bias or unlawful discrimination.
www.financial-ombudsman.org.uk/publications/ombudsman-news/48/banking-closing-accounts.htm
It'd be worth someone digging out the business banking code...
Incidentally banking is not the same as selling potatoes or providing print services or whatever, it has significantly more rules on what you can and can't do due to the public detriment if banking services are not available.