Ah. Thanks. So when the Aera reports '3D Differential' (which the user manual assures me that it can) it is receiving WAAS not DGPS.
Less confused now, thanks!
That also explains why my old Lowrance Airmap 1000 never got WAAS either, if it doesn't work in Europe.
Tim
PS Hang on, though,
What is SBAS? | EGNOS Portal says WAAS and EGNOS are interoperable and a receiver which can get one can get the other; and
Receiver list | EGNOS Portal lists the Aera series as compliant. Confused again...