As promised, final update (hopefully!) on the Spanner. There have been no further instances of the error appearing, thus:
The Amber Spanner alert which occurred early in journeys and was reset by turning off ignition and re-starting was fixed by Ford Service after a full read-out uncovered an airflow DTC (Diagnostic Trouble Code). This was flogged and the actual tech report states "Air filter clip not clipped in thus air filter drawing in air under seal. Re-clipped and all fine now". A further DTC concerning battery did not reoccur upon test after the module was reset.
This is interesting. Now I have the actual words, it looks like the air filter body clip was not correctly secured, ironically after the dealer's pre-sales service. I wonder if this a useful warning?
Change filter, see Spanner, check cover clips!
Thanks for your interest, all,