Don't worry Trevor I'm changing both rear shocks and top mounts as a matter of course. Won't have time to change the springs due to the short time from for the next show but I'll add it to the list.
Welcome to the forum you'll find the members on here are a friendly and helpful bunch. My brother has driven both the 911 and r8 and he says the R8 is the better drivers car.
My advice would be to get a diagnostic check carried out. Does it happen after short journeys or long journeys. Whats the weather conditions when it happens ie hor or cold. It's probs worth trying to establish if there is a pattern to the issue.
On the more technical code readers it should be able to read historic codes. As the car should store them once they appear even if the car has managed to find a way around the problem. I'd still be getting it checked if it were mine.