ok the aerator died, the motor runs but the blades dont turn so i reckon the drive has become detached somehow. as i am not mechanically minded i wasnt about to go looking at its innards, so i rang screwfix on the off chance and blow me down with a feather they said no problem bring it in and swap it.
i felt sure they would make a fuss and blame me for overworking it etc. but no drama or anything, half an hour later i am putting together a new one.
well done screwfix.