I have an error code on the dash of my Marea(2002 model) that looks like an orange coloured engine block. I don't have the manual so cannot interpet.
It came on for approx 45 mins of driving then went away again.
Does anyone with a manual know what it means?

That is a new symbol not in my manual. It is a standard iso design for engine management system malfunction. If it only stays on for a short period of time it should be ok. If it stays on it will need checking.

What was the weather like, (if it wasn't cold and wet, why not )

These faults can be hard to trace without a diagnostic. Just give it a general check for connections and cable wear for now.

If anyone can come up with the manual definition of this indication you will earn a rep point.