I have the factory printed manual. If you look closely, I think you will find that the relay module you described is shaped like the letter "L", upside-down, and extends through the top of the firewall into the space behind the instrument panel. I found iI easier to access the hidden relays from the passenger compartment than to retract the module up from the engine side.
Note that I've assumed a "late 99" V70 is still the S70-based model. If your vehicle is the "new" V70 based on the S80 platform, the fog light relay is also mounted behind the instrument panel, on the Central Electronics Module (CEM). I can send you drawings of the fog light relay location for both models, as JPG files, if they are not included on your CD manual.