i feel for you man, its easy done
What are the guidelines on speed that decide whether you get a fixed penalty or a summons.
The current guidelines from the Association of Chief Police officers (ACPO) are:
So up to 79mph you should be just told off, 79-95mph is a fixed penalty and 96mph+ is a mandatory summons to appear in court.
http://www.speed-trap.co.uk/FAQ/FAQ.htm
so from this it looks like over 66mph in a 40mph speed limit would get you a summons, so its probably 3 points and £60 fine