Many thanks for the advice Ant and Bob.
In the end I got a company called LCM to “polish” the fuel and put it back in the tank. That was not easy since the tank tends to overflow if you remove the fuel gauge diesel level detector to gain access. I am planning to fit a MFP2 diesel purifier from MLS between the tank and primary filter to prevent further episodes if the bug comes back. We only had a tiny bit of water in the fuel and we still had a lots of the bug. The purifier has a drain tap to remove water and diesel bug on a regular basis, before it gets far enough to block the primary filter. I might write all this up for the magazine once it is all done and working.