The Telegraph today reports that motorists done for speeding are frequently having the incorrect offence code of SP60 applied to their licence rather than the correct SP30 which is normal for offences on non-motorway roads.
The 30 and 60 in the offence code do not refer to the speed limit on the road at the time, they indicate totally different types of offence. Insurance companies are not so keen on the SP60 code and so if you have been done for speeding you should ensure that you have had the correct code applied to your licence. Paul Smith at Safe Speed has a table of offence codes here:
http://www.safespeed.org.uk/pr234.xls
Note that SP60 doesn't appear on this, probably because it is an "undefined" speeding offence which is probably why the insurance companies don't like it.
Worth getting it sorted out if your offence code is incorrect, some companies may even refuse insurance if the offence is an SP60, and if you have been paying extra in insurance then you may have a case for compensation.