Ian,
Belle my 2014 Roadster has relays that rise from the connection board. I found this out after hitting a bridge expansion joint in Holland where my indicators stopped working & the power steering stopped.
I pulled over & the car then wouldn't start.
I checked the relays & pushing in the fuel pump relay (it powers the ECU) all was restored.
Relays were replaced to be safe & I now have foam on the inside of the fuse box cover to stop them coming loose.
My 2005 Roadster after a drive in heavy rain wouldn't start. The immobiliser light stayed on. Later I found out that the fuel pump relay had shorted out & that powers the ECU. No power on the ECU & the immobiliser stays on.
I hope that helps. I'm no auto electrician but it seems to work.
