c5 headlight problem?

Hello

I am having a prob. with headlight for above, I have changed the Xenon DSR gas filled light, as it had shattered. So I thought it would solve the prob. but it hasnt as the headlight bulb is flashing three times and then goes off. I want to know is the balast easy to change, or do I need to get a complete headlight for the citreon.

Or should I take it to auto electrics to check the relay. Please can anyone have any suggestions, as I need this rectifed as it is nearing MOT. time

Any suggestions, or have anyone had a similar prob.
Gary Cooper