Check multiplug at rear of headlight.
Check:
(a) It's not loose or not pushed home.
(b) It hasn't melted or burnt out. The multiplugs on MICRA headlights often melt (possibly only partially) and this can result in high beam staying on. Due possibly to headlights being left on for long periods while the car is stationary with no air flow to cool the headlight area.
A new multiplug can be got from Halfords - it comes with 3 leads attached which will have to be joined to the existing wiring loom - a fiddly sort of job - make sure the joints are properly sealed/insulated afterwards.
