"Is that why I got done doing 32mph in a 30mph zone,New Judge?"
My FIL also got done doing 32.
Then you are both unlucky.
My statement should have said enforcement normally starts at 35mph. Whilst any excess over the posted limit constitutes an offence most police forces comply with the Association of Chief Police Officers' Guidelines. Each force produces its own policy but I don't know of any who do not generally comply. Here, for example, is Cambridgeshire's policy:
https://www.cambs.police.uk/roadsafety/docs/201305-uoba-joining-forces-safer-roads.pdf
Section 9 gives the details but the document does mention that any excess can be prosecuted.
And here's an RAC document on the topic:
http://www.racfoundation.org/motoring-faqs/enforcement#a2
The margin does not mean a new, higher limit exists. The leeway is designed to reduce the number of frivolous challenges that might be made on the basis of inaccurate measuring equipment or methods.