I've just received a fine from the hire company for getting a ''speeding ticket''' !
I presume you mean an admin charge from them, for the admin of replying to the NIP (well S172 request on the same piece of paper) with your details?
Perfectly normal.
As these were variable speed cameras on the motorway and speed limit changed a few times, can I not question the credibility of the speed cameras (for example are they accurate) ?
Question the 'credibility' no, of course you are free to question the accuracy by declining any out of court resolution offered (course or fixed penalty) and then defending it court. But if you fail to cast 'reasonable doubt' (and odds on you will fail) it will cost you about £1000 for exercising that right versus circa £100 for the out of court resolutions you are certain to be offered. Unless you can identify specific issues you may be able to use in a defence, it's foolish to just 'hope' you can find something.
Yes, admin charge
OK - so they don't have to prove that the cameras they used were accurate/valid and that the speed restriction wasn't an anomaly on their part, before going to court ? Are these not reasonable questions to raise, before going to court?
If the cameras say were not perfectly aligned they could give a mis-reading ?
and question whether the speed restrictions were correctly applied between the different areas where they had restrictions in place - the speed restrictions seemed to be very inconsistent across the stretch of the motorway, on the narrower temporary lanes whilst motorway road works were taking place.