Regrettably this is a 'grey area'. The Bank will say that you agreed to their terms and conditions when you opened the account. Somewhere in the small print will be a term authorising this charge.The contrary argument is, in essence, that this amounts to an unfair contract term.
As in most areas of civil law, pursuing the claim may cost more in time and money than the claim is worth.There are firms online that claim to help but they are really only interested when the charges are sizeable (and they claim 25 per cent of the sum recovered, too!)
The best track is to try to find a bank that won't do this or to sell your bank the idea that it is not in their best interests to annoy you by such pettiness e.g if you are a student whose future career may bring the bank big business (They'd be daft to irritate a future solicitor , considering all the funds that solicitors have control of !). Almost needless to say this, but you'll get a result if you are like a friend of mine who was charged �30 for exceeding his personal �20K limit by �18. He told the bank that he was minded to pull all the business accounts there that he was in control of. They instantly remitted the �30 !