Disconnected battery for ten minutes-nothing
Tried spare key-nothing
Reset BSI (clutching at straws)-nothing
Still got the key symbol and display warning
Called the double A on the girlfriends card.
When he looked at it the immobiliser warning had gone but wouldn't start.
He plugged inthe OBD2 interface and said "aha!" Pressed the inertia switch under the bonnet and it started.

He asked if I'd had an accident or bump recently which I haven't and also said if you slam the doors it can do this.
I have had a problem with the front passenger door central locking recently and a good slam has cured it. Maybe this has caused the problem.
Cheaper than taking it to Peugeot.

Gave the fella a drink for his diagnosis tho!
Might replace the immobiliser transponder ring tho as this can cause a problem.