Okay, at the risk of replying to myself
, a small update.
Reloaded at Lorient, headed back down to Afrika. Sank two large cargos on the way, in foul weather - heavy precipation and fog, in the dark, which was great fun. Got to EK78, observed the same muiltiple spawn / reporting going on (with a new report every 7.5 hours or so, went on for several days until there were at least 15 contacts showing!). Now headed back North slightly feeling happier than I was.
Cheers for the comments and advice.