Also be aware at least on a 2006 Roadster the relays also supply power to the ECU. Mine failed but lights etc worked , only the ECU wasn't working & the starter wouldn't turn over. . Despite having spares in the car neither I or the two mechanics who looked at it dreamt that it was the relay. we though it was the ECU or the immobiliser.
Now that's a good point, looking at the diagram on the cover it actually says ' ENGINE / IMMOBILISER RELAY ' so you may be right and I should change the label.
