Horn and wiring

I am rewiring my headset after respraying it top and bottom. Someone has fitted a new ignition switch in the past, however the light-indicator switch is made by Leonelli of Barcelona. I have fitted a SX 200 Headlight assembly. In short none of Sticky's wiring diagrams help on this one. To help I am using a good strong 12 volt battery as the power. I am not using the stator wires whilst I am wiring. I have ignition and spark. I have dip and full beam, rear light is ok, so is the brake light. The horn which was ok now sounds like a wet fart.
Do I need the festoon side light for an MOT if I have dip and main beam.
The horn, could this be just the weak temporary joints or bad earth. Could it be that I am using a temp' battery on a AC Horn.
With all these bits that do work OK, why have I got the Yellow, Blue and Black wires from the ignition not connected to anything.
Happy Easter
Do I need the festoon side light for an MOT if I have dip and main beam.
The horn, could this be just the weak temporary joints or bad earth. Could it be that I am using a temp' battery on a AC Horn.
With all these bits that do work OK, why have I got the Yellow, Blue and Black wires from the ignition not connected to anything.
Happy Easter