Dimensions comes with compatible BACS export formats for most major UK banks, however from time to time, these do change, and you may find the format you need isn't included if you currently run an older version of Dimensions.
Your bank should be able to provide you with documentation that describes the format the file should be in. If you're having issues locating a format that matches the documentation your bank has given you, please raise a new case online and reference the title of this article as well as attaching the documentation from your bank. You may be advised to upgrade your software.