Black Sea Campain Issue

Having an older pc I recently loaded the Black Sea Campain which did speed up the loading time as suggested in the GWX manual - great.
But, at the end of the first mission, after returning to base and reloading torp's etc, I went to start my next mission and I got the message "base changed to Brest" - which is outside of the campain. I would like to remain in the Black Sea region for the rest of the campain. Any ideas, guys?