Yes, I found out that the mk1.5 lx is not wired up for fogs as standard if they are not on the car!
Trust me, I had the bumper off, lights off, and there is no loom for the fog lights.
I did it though, but I had to make up my own wiring loom, and connected it directly to the new light switch I had to buy with the front fog switch on it...
I found a guide from a US forum, which gave a rough guide, I'll try and find it for you..