Problem with full beam headlights

Ok this is a new one for me, has anyone has any kind of similar experience or can they reccommend any kind of solution:
On my way down the A31 on saturday at about midnight i was driving along (the road was un lit and it was wet outside as it was raining) when i came upto a town, so i dutifully reduced from 60 to the posted 40 mph and decided as it was a town i needed to turn my full beam head lights off. So i did so and merrily cruised through the town, once i was out i needed the full beams on again, so i pulled back the control arm, heard the normal clicking noise it makes but to my horro my dipped headligths turned off (as they shoudl) but my full beams didnt, i quickly flicked the control arm again and my dipped cam on and tried in vain once again with no luck, as it was midnight i decided to leave it and limped home at 40 mph (fortunatley i knew where i was going and i wasn't far from home)
So has nayone else experience this rather strange event or fixed a probelem like it.
After i got home i went out to the car about 30 mins later and tried the full beams and they worked, the rain had gtten and little lighter so im thinking water causing mayhem.
Any ideas guys and gals?!?

old electronics! sometimes i need to give me lights a little bit of a nudge to get them working, dont worry about it, if you went over a little pothole im sure they woulda turned on...you can rewire them if you know how, with more conductive wires

Check your fuze box mate for water that may be leaking on to it from the windscreen or scutle area , common problem


Cheers …………