50Kph is 31Mph. Unless we are in a 20 limit it is legal everywhere! Speed limit + 10% + 2Mph is still the calculation used to allow for faulty speedos etc. Dunno about anyone else by the difference between my speedo and my sat nav seems to confirm that this is not far out.
That is 'guidance' only, not the law.

For fuller details see: Here where it clearly states:
Scottish police have decided not to follow the guidance at all, and will prosecute drivers for exceeding the limit by even 1mph, regardless of any device tolerance.[3] There is also talk of a review of the guidance, which was first issued in 2011, to take account of developments in speed enforcement technology.