Mine do this:
In my case I work about 60% of days so I get 60% of bank holidays. I workout my annual leave entitlement i.e. 60% of my full time equivalent . So I get 'X' number of normal leave days and 'Y' number of bank holidays.
Then if a bank holiday falls on a day I normally work I deduct this from my Y figure.
If a bank holiday falls on a day I don't work I am expected to take a day off work close to the bank holiday and deduct it from the 'Y' figure.
Interested to hear other approaches.