AMS,
You wouldn't need to declare it and it won't show up on any disclosure form.
Even if you were charged with the offence, it doesn't mean you are guility of it. You would need to go to court, and if you are then proven guility of the offence it will be added to your record.
The reason fixed penalties turn up on your record isn't because you are guility of the offence, it's not a criminal conviction it's pretty much a settlement to avoid you having to go to court and the justice system from having to take you to court.