hi, i had/have a similar fault on my 03 147, the offside front side light kept blowing...turned out to be the body computer, luckily it was under manufacturers warranty but i think it came in at about £450. I have just returned from a tour overseas to find the same problem. I thought as a new computer had been fitted it may have just been a bulb....got a new one fitted, blew staight away. Just hope the garage that fitted it in april provide a 1 year parts warranty...otherwise its a bill i dont really need before xmas! lol.
hope youve got the problem sorted.
If anyone else out there knows what the problem could be...if it is in fact the body computer, again on mine especially lol...please feel free to add!