The error you may get on starting the server reads:
"Failed to initialise sort code validator. Ensure the ISCD files exist in the directory D:\BACS.IP\n.n.n.nnn and are valid."
The problem where BACS.IP is unable to access the ISCD files is caused by multiple .DAT files in the ISCD sub folder (by default 'C:\Program Files\DIP\BACS.IP\n.n.n.nnn\ISCD', where n.n.n.nnn is the version and build number) of the current build of BACS.IP.
To resolve this issue, please remove or rename all but the latest .DAT file in the ISCD folder.
Once you have done this, you will need to restart BACS.IP, including the server application. This will ensure that when it restarts, BACS.IP will only attempt to read sort code data from the new directory file.