OBD diagnostics scanner
It turns out that my car has a proper Malfunction Indicator Light (MIL), which is the amber engine icon on the rev counter. I went out for a run earlier this week, the first time since November. As I was coming back down the A127 the light came on! The engine seemed fine, but I limped home and pondered what to do. These situations are where the owner's club really comes into its own. A quick message on the local WhatsApp group and the next day club member Chris Collins very generously came round to diagnose the problem.
Although we could not get Easimap to connect to the car, a standard OBDII scanner worked just fine. Turns out the warning light was due to a flood of speed sensor warnings. The speedometer had been jumping around and I just needed to adjust the sensor gap on the rear wheel hub. No major drama!
I've now purchased an OBD scanner that plugs into the port which is located behind a rubber grommet above my right knee in the cockpit.
£50 from Halfords, but it works fine. It gives both stored/pending error messages and also live data readings. Hopefully I won't have to use it very often, but a useful tool nonetheless.