Yes, I did just tap into 83b using a skotchblock. The Haynes wiring diagram shows this wire just running directly to the fog lights so I just ran the wire directly to the fogs and all is fine. Again, looking at the diagrams, there is no additional fuse for fogs, although I did put a 15amp fuse inline. Not because it is needed but to protect the light switch from damage should my home made harness somehow short out. That way my fuse cops it before the switch does. I picked up my grounds from within the engine bay. The nearside one is grounded to the -ve terminal of the battery and the offside one is grounded with the nearside lights to an earth point near the offside front of the engine bay.
Here is how I got the wire out to the engine bay. Maybe not the best way but I didn't want to drill holes and I couldn't find anyplace or grommet I could just shove it through.