1. What is the law on driving with it out? I've been pulled a few time in the past and just got told to get it fixed but if I get pulled again it could be a fine¿
Note that it is illegal to drive with a headlight out, even in daylight. You might ask 'how would they notice?', but it is still illegal.
2. It keeps happening!! The drivers side dipped is constantly blowing every 1-2 months what could be causing this?
I used to have this on a Cougar. The garage said 'nothing wrong...you are just being unlucky...bulbs do wear out after a time, and sometime you get several reaching their end of life together, etc, etc'.
This was, of course, nonsense as I was losing a bulb every six to eight weeks, always at the front of the car. That's not normal.
What you could also see was that the voltage was not very stable at idle - if it was dark, you could see that the dash illumination (eg, radio display, speedo, etc) and the lights would go up and down a little with the bass in the music. there was an alternator wiring problem with the cougar , generally, and Ford had an additional harness (probably a wire, but it sounds as if it costs more if you call it a harness) that could be retrofitted to cure the problem.
With that fitted, it went down to blowing a bulb every couple of years, rather than couple of months. Ford garage never admitted that there was a fault that they should have done something about.
Anyway, if there is any sign that the voltage is 'wobbling about', even at low engine rpm, then there probably is a problem with the wiring, and things like the alternator earth and battery earth are suspect. In that case, it is probably as easy as adding another, thicker gauge, piece of wire, but it might be a bit difficult working out where, exactly.
In the interim, you could get yourself a supply of cheap bulbs (not very nice, but...) and try to avoid switching on the lights before you have got the car started.
Also note that 'smart charge' does put the charging voltage up a bit, and you probably want to check that your battery can cope (a suitably specified silver calcium one, rather than an 'any old rubbish' battery) and that the terminals there are in good shape.