I have been doing work in this area just today so its quite fresh, what year car is this for a start?
fuse 7-8, the bottom one only gets power when the lighting switch is operated so first question, do you have sidelights all round and the instrument cluster on? if so then you must have power at the switch if not then the problem is before there. The feed to the switch is a brown wire which should be constantly live as it comes from the same source as the feed to terminal 3 via the starter solenoid, there is no fuse!
A multi meter on terminal 3 (left side 2nd one down) would be a good start if you have 12v there then try turning the switch on to see if you get any voltage on the bottom terminal same side (7).
The wiring diagram shows the brown wire as being commoned up on terminal 3 with the incoming feed from the battery, mine is so I would check that is on yours and that it is solid, mine broke off today as I was removing it for repairs (see my project thread as its all about what you are doing).
I made an idiots guide that I will try and upload for you now, it should help you a lot!
Edited by CityEPete, 28 December 2013 - 06:32 PM.