Update... I hope.
Borrowed a reader from a colleague. The 1 code mentioned a Knock sensor. P0330 I think ...
Car was still driving but in limp mode I think. ( Never happened to me before...! )
Having 'researched' on the internet, I tried a 'reset' by disconnecting the battery for a few minutes.
Reconnected the battery ( found the battery strap that secures it very loose. ).
No amber warning lights. Driving normally.
On its first re-start I need to hold the throttle pedal down as it idled, but having now driven about 30 miles, it's all back to normal.
Fingers crossed it is.
Why? I DID go through a large flooded puddle too fast. Water ingress?
Don't know. So fingers crossed. Limpness gone.