Here's an update, and this, apparently is how the Plus 4 GDI should behave.......(I've consulted my Guru).
Key into ignition.......two seconds and two flashes and it disarms.
Leave key in ignition without turning..............
Wait 30 seconds approx, and the light goes 'flashflash flaaaaash' So dot dot dash......and this repeats every thirty seconds while the key is in the barrel but the engine not turned on.
Mine is now doing this, so hopefully it's sorted!
DaveW '05 Red Roadster S1 '16 Yellow (Not the only) Narrow AR GDI Plus 4