Firstly, assuming that you are convicted of speeding, the court is required by law to order your licence endorsed with either 3-6 points or ban you from driving for any period of time, unless they find that there are special reasons not to endorse (which is compelling mitigation regarding the commission of the offence - any argument regarding whether or not the restriction was pointless at 5am isn't going to cut in for SRNtE).
The magistrates have guidance on sentencing within those parameters which they are permitted to deviate from but are required to justify doing so, and are often reluctant to do so. 66+ in a 40 limit is sentencing band C in the guidelines which you are presumably aware is 6 points or a 7-56 day ban.
Many people, including some magistrates, think that "exceptional hardship" is restricted to avoiding a totting-up ban - but exceptional hardship is simply the only ground on which a court can avoid ordering a totting-up ban if the offender tots up to 12 points. A court is entitled to consider any relevant mitigation in other cases. Whether they will be inclined to do so is another matter.
To "argue" for less than 6 points, you would need to request a court hearing (or hope that the SJ reads your mitigation and decides that the case is not appropriate for the SJ process), and present your argument in person. Technically you could present your case by post - you will not be required to attend unless the court is considering a ban - but technically you could also try to win the lottery by weighing half a bag of cake-mix.
Stepping outside of the streamlined process by requesting a court hearing will delay matters. You could delay them further by pleading not guilty, but any sympathy that you might be hoping to engender within the bench would tend to evaporate quite quickly.
In the past, I have had some vicarious "success" with mitigation where the "paint-by-numbers" perceived seriousness of the offence is greater than the actual seriousness.
On the face of it, you were doing 30mph over the speed limit, which is a significant amount. Assuming that the limit was signed correctly, logically you were either not paying attention (which would tend to make the offence more serious), or you deliberately broke the law by some margin.
The law is the law. Other than variable speed limits, speed limits apply 24 hours a day, regardless of traffic, etc.. If there was little to no traffic and the rationale behind the reduced limit was not present at that particular time, the speed limit still applies and you had no excuse for exceeding it.
However, having fallen on your sword regarding the above, the bench might be amenable to considering whether the public safety aspect of the seriousness of the offence, having already fallen on your sword regarding the blatant criminality for which you have no excuse, is reflected in the sentencing guidelines, and whether the wider effect of the guideline sentence matches the seriousness of the offence.
What won't help you is that being a professional driver will itself be an aggravating factor for driving offences.