by no means a hard fast rule. But i've had my fair share of speeding points in the past. In my experience, if it's a patrol car with an actual police officer in, they chase after you, pull you over and give you the chance to talk, explain etc.. then issue you a ticket.
If it's the actual mobile speed camera fans, or fixed unmanned cameras, these just send you it in the post. I personally wouldn't worry.
Exception to the rules and all that, but what else can you do other than sit and wait and watch the postman every day for the next 2 weeks ?