I am convinced now that it's just one main fry - seen him quite regularly over the last few days. Is getting quite brave, meandering along the front middle of the tank glass, pottering along on the bottom eating stuff. Is nice to see him out and about. He has been eyed by the big male and found to be not worth eating as a meal and left alone again.
The eggs that I saw on the bottom of the wood scrap have either hatched or been eaten as they are now gone.
Found another egg on the bottom of the driftwood when I took it out to add a plant, and another egg in the cabomba I pulled out, so I dropped that into the middle of the new christmas moss.