The Association of Chief Police Officers (ACPO) issues guidelines to forces to assist them with speeding offences.
The starting point is that offences are not normally enforced unless the speed measured reaches the “enforcement point”. This is (speed limit + 10% +2mph) and in a 50mph limit this equates to 57mph. Up to this speed normally no action is taken (although a formal caution is sometimes issued). Above this speed there are levels which trigger either the offer of a speed awareness course (SAC), a conditional offer of a fixed penalty (FP), or a summons issued for a court hearing.
Where the limit is 50mph, 58mph would normally mean a SAC is offered, 59mph would normally mean the matter is dealt with by way of a fixed penalty and 76mph would trigger a summons.
You should note that these are guidelines only and individual forces may have different policies which vary slightly. SACs are not offered in all areas and are not normally offered where a driver has committed a second or subsequent offence within three years of the first. You will also note that I have used the word “normally” throughout. Once an offence has been alleged (and an offence is committed if the speed exceeds the limit, not the enforcement point) it is up to the individual prosecuting authority (usually a “Safety Camera Partnership” in the case of offences detected by a fixed camera) how to proceed.
If the guidelines are followed in the area where you were detected you should receive a fixed penalty offer providing there are no aggravating features and you have less than nine active points on your licence.