First and foremost the said police officer has to caution you, basically do you recall him saying
"you will be reported for the consideration of the question of prosecuting you for.... Excess speed/dangerous driving etc...
If not then he has maximum 14 days from the date of the offence having come to light, in your case the day he spoke to you to serve you with an NIP,
The 6 months issue is how long it could take from the NIP being served until it goes to court, efficient plods can do it in 6 weeks pending court availibility.
Did you see or did he offer to show you video footage, what type of bike was it, did his speedo have a calibration sticker onthe speed dial???
Sounds like you were either in such a shock for being caught you can't recall any details or, and hope it's the case he just wanted to put the frighteners on you!!!
Eitherway, use your mirrors more and situational awareness
good luck