Thank you for your question.

You raise a number of points here.

Firstly the fact that the road used to be a national limit is irrelevant, it is now a 50 and is signposted as such.

Secondly, you must have been stopped at the time, as it is a hand held device and not a camera. That means that a section 1 warning would be given. That rules out the need for a notice of intended prosecution to be served as a section 1 serves that purpose. That means that a prosecution must be started within 6 months of the offence date, In your case that means the court date must be before 26th November, I make an assumption that it is, given you've received a citation. Avoiding the court date will make no difference.

You also seem to accept that you were doing the speed that is alleged so in reality there does not appear to be any point in pleading not guilty. The only likely outcome to that is a finding of guilt after trial and a higher penalty. Pleading will result in 3 or 4 points and a fine of about £120 to £150. Go to trial and get convicted and expect 4 or 5 points, maybe even 6 and a fine of £200 to £250.

Not all doom and gloom though. There are faults with the Unipar SL700 and it's operation in Scotland. It is a device that was developed for use in England and has to be adapted to be operated in accordance with the law here. The adaption is made by the operating officer and is regularly not done, especially in Dumfries and Galloway and Strathclyde force areas. I am not prepared to divulge on a public forum, however, any more details of the adaption. You will appreciate that this is information that normally commands a significant fee and I am not prepared to divulge it for the fees charged on JA. Most competent Road Traffic Lawyers will know this defence and can advise you accordingly.