Free Traffic Legal Advice

The request for driver identification should be answered within 28 days. Otherwise a more serious offence is committed.

The clocks went back to GMT on 27 Oct, so if the offence was committed "well before the clocked [sic] changed" you may have already missed the deadline.

If the time on the photos clarify that they are in GMT, then, IMO, it doesn't provide you with a defence, regardless of whether the offence was committed during BST or GMT.

A NIP cannot be dismissed. It is simply a notice telling you prosecution is being considered.

You must respond to the request for driver's details by stating who was driving at the time mentioned on it. The police have no obligation to provide any photographs at this stage. Any provided are as a courtesy only.

Once you have responded to the request the police will decide what to do. They will almost certainly offer a course for that speed if you have no done one in the last three years (measured by offence dates) or otherwise a fixed penalty. You could try pointing out the discrepancy to them but I would only do that only after you have made your response. 

If you want to challenge the allegation you will have to decline any offer they make and plead not guilty in court. I would suggest the police will be able easily o explain he time difference and the court will accept that explanation. The cost of such failure will be high - at least somewhere in the region of £1,000 for most people.