OK, so took the car on its longest run TD today, 90mins each way.
Tested as follows: As to the P2404, if you get to highway speed and set cruise, does it hold? YES
If so, if you tap the brake pedal, does it cancel the cruise? YES
If both work, then the code is baloney. OK cool, that's a relief then, will just move on and not give it further concern as drives as it should and without fault.
Many thanks to all that have posted here, much appreciated.