Hi
Or you could just call a web service that will validate your bank sort codes (and account numbers)
That way you don't have the hassle of updating your sort code database (and the modulus checking rules that go with it) every month or so.
Try Unified Software. You can download a jar file from the developers area.
www.unifiedsoftware.co.uk/developers/cookbook/java.html You can be up and running within a day or two.
Cheers
Phil