Hi
i also got a ticket back in june (not local to somerset, unfamiliar with road) and have completed a speed awareness course today to avoid the points and fine! £95 later ..... i was on A370 (winterstoke road) industrial / retail area near next and asda, it was a mobile unit, i did see it but was unaware of what the speed was.
Road is not definately not marked as 30 (have since got family member to check i would have gone to court and disputed it if i was local,) in direction i was coming from and it was a dual carriage way, i assumed it was national speed limit, however as heavy traffic was recorded as travelling 35 mph. However i did learn a few things on speed awareness course. Hope this helps