Have a look here.
http://www.pepipoo.com/
Look for the stuff about making "PACE" statement, If you have the patience it might work out if they havent closed the loophole.
If it was me though and I knew that I was definately speeding, then I'd just take the fine / point.
If your going to do the PACE you have to follow the intructions exactly, but it might backfire on you and you'll get in deeper hot water ( possibly )