Hello Paul,
I know yours is a Peugeot problem but
I would check all the wiring around the engine and battery area.
We have had 2 citroens in lately on siemens management systems with broken wiring.

The last one the wiring loom for the Cam shaft sensor had been trapped/pinched on the flange between the EGR pipe to manifold.

This vehicle had had all sorts throne at it by another garage, from 2 sets BSI suites/locks and all, fuel pressure rails etc etc.
Ebay did well out of it though

Somebody at sometime had been a bit hasty under the bonnet
So never be surprised to be surprised

Ian