I received a NIP to say I was doing 36 in a 30, in the West Mercia area, on ‘manned equipment’.
No, you have not.
However, the photo only shows a zoomed in image of the car and it is not possible to see where along the road the alleged offence occurred. The road has sections that are 30, 40 and 60 and if it was in the 30 then fair enough, but there is no way for me to see. Does anyone have any advice if it is worth exploring this with the Police?
There is no obligation to disclose any evidence to you at this stage. Some forces seem to send out close up photos of the vehicle to pre-empt requests for photos to help to identify the driver. If the allegation is that the (as yet unidentified) driver of the vehicle was exceeding the 30mph limit, then the allegation includes the vehicle being in the 30mph section when the speed was recorded.
The police are under absolutely no obligation to prove anything to your satisfaction at any stage. If the matter were to proceed to a contested trial at court, the police would need to prove their case to the court beyond any reasonable doubt, and you would be entitled to see that evidence, and challenge it if appropriate.
You are proposing to go on a fishing trip on the off-chance that the police have made a right horlicks of it and caught your vehicle at 36 in a 40 or 60 limit. Whether the force in question would entertain a request to satisfy your curiosity is a matter for them, but I would expect that their response to such a request would be able to be accurately summarised in two words, the second being "off".