Yes, magistrates can fine you up to £1000, plus "victim surcharge" plus prosecution costs. It's the cheapest option.
Indeed. Although the likely fine (provided you plead guilty) is a week's net income (capped at £1,000) then reduced by a third for your guilty plea. The surcharge is 40% of the fine and costs are around £90. So the most you will pay (if you have an income of £1,000pw or more) is a bit over £1,000.
However, the deal breaker for most people is the endorsement code (MS90) that goes with the conviction. This is particularly nasty as far as insurers are concerned and will see considerably increased premiums for up to five years. For most people this is a far greater penalty than the fine.
I would be able to include with my NIP response copies of accommodation bookings and petrol receipts to evidence that we were holidaying.
There's no point in doing that. All the police want to know is who was driving. If you say you do not know, they
will prosecute you for failing to provide the driver's details. There is no "might" about it as suggested above. That evidence may help if you decide to defend that charge but the police will not consider it; that will be done in court. There is a statutory defence (i.e. one written in law) which says this:
"A person shall not be guilty of an offence...if he shows that he did not know and could not with reasonable diligence have ascertained who the driver of the vehicle was."It's a tough hurdle to clear (if it was easy everybody would do it) and the court will want to see evidence of the "diligence" you employed to find out who was driving. From your description that might be difficult for you. Whilst there are occasional success stories, I think defending that charge more often results in failure than success.
I would suggest the pragmatic way to deal with this is to obtain the photographs as suggested. They are very unlikely to help you identify the driver but the main reason for seeing them is to make sure nobody else could. If, say, you accepted you were driving but a photo showed clearly a male driver, the police would probably ask you to "reconsider" your nomination and it would be best to avoid that.
Then decide between you who was most likely to have been driving, return the form and take the course that is almost certain to be offered.
It's an unfortunate consequence of this legislation that often sees a far harsher penalty imposed for telling the truth than perhaps declaring something that you are not certain is true. There are various schools of thought that argue the legitimacy of this course of action. Strictly speaking, if you don't know who was driving you should say so, but with the potential consequences of doing that being so much harsher, it is little wonder that most people take a pragmatic approach.
So long as the police do not suspect one of you is trying to gain an undue advantage (for example if one of you was on nine points and you named the other just to avoid him or her facing a "totting up" ban) and so long as the photographs do not clearly suggest your nomination is incorrect, the overwhelming likelihood is that your case will simply make its way through the "sausage machine" without trouble.