Since you are in the trade I am surprised you don't know a Peugeot chappie.

T'm going to guess here as I don't have acces to Peugeot wiring diagrams at the moment.

But as far I recall the starter relay control terminal is pulled to ground by the BSI,

So scan the body systems interface for faults.

But to help me I will need the build code number from the sticker on the front door "B" pillar and I'll check the diagram.

Okay,

I have access to Peugeot wiring diagrams now but will need a whole lot more information to be accurate,

Make:Peugeot.

Engine:? what size/fuel type

Year?

Build code number?

on the sticker on the door lock pillar.

And there's a difference in the wiring from model to T3 model.

But assuming my first guess is right the starter relay in the engine bay fuse box IS controlled by the "BODY SYSTEMS INTERFACE"

So if it's not pulling the relay coil to ground then the relay won't operate or click on key to crank position.

So I'm back to suspecting the BSI.

check it for water ingress,

common on Peugeot's