New 197 owner - hello to all!

Hi folks,
Picked up a Nimbus 197 today after 3 years in the doldrums driving a yaris (needed cheap/ hassle free motoring for a while), previous to which i've had a few quick cars (starlet turbo, corrado 16v, s13 200sx, 93 JDM impreza wrx)

well chuffed with it! handles like a go-kart and pulls like a train! - has reminded me why i like cars!!

when i picked it up, the reserve light was on so on the way home ive put £50 of v-power in it, after a spirited drive this afternoon the engine managment light has come on, with the spanner on the dash and "check emissions" next to the clock.
engine wise, nothing has changed, drives exactly as it did before it lit-up - no mis-firing, hesitation, struggling to idle, anything.
ive got an obd reader on order so will see what code it throws out, in the mean time, any ideas?

cheers
Josh