Level3 with DE problem.

Headlight dipped/main failed yesterday on drivers side, I thought it would be a great time to do a bulb upgrade as the DE type headlamps aren't exactly great. Side light on same side went out tonight. Not being a great believer in coincidence, I gave the headlamp unit a nice big slap... everything came back on. Thanks to the speed and ease of the internet, the new bulbs are already ordered! However after repeatedly starting/stopping the car, turning lights on/off and my technical slap it appears to be a proper fault. At first I thought bad earth connection, but something's telling me there's a lot more to it.

Anyone experienced this before???