Car failed the MOT yesterday morning on two minor items. Rear brakes binding (my fault, I'd overdone the handbrake adjustment the previous evening) and indicators not flashing quickly enough. That latter one turned out to be the battery being flat combined with the alternator not generating the required voltage at idle as it was fitted with an extra-large pulley to stop it getting very very hot at high revs on the race track. I refitted the smaller one and it now runs a bit hot but it does charge the battery and the indicators work. Got the car back for its retest before the end of the day and it passed no problem that time.
It's now taxed for the next six months and I've done about 30 miles today as an initial test run and all seems fine. The only problems being that I'm now deaf (the racecar is very noisy inside) and it's misfiring above 4500 revs under load but I suspect that may have a lot to do with the fact that I'm running it on 95 octane fuel as an experiment and it may be "pinking". I think I may need to go back to the more expensive variety of fuel. I may try fiddling with the ignition timing as well to see if that helps in the meantime.