In reply to IainRUK:
Yes everything I've ever read inc the 3000's book is summit to summit. My own times were from car to car, the mountains themselves were the aim for us not the times so it didn't really matter to us. If pushing a timed crossing though it'd make sense to preserve energy and use the train, clock starts when stepping off the trig point in my eyes.
I'd reccomend the north to south route, prob most of interest to those wanting to do some scrambling and finish on the highest peak rather than start from it <as climbers this sort of made more sense to us anyway> Logistically its a pain though, 2 cars needed and a bit of running around. We broke it down to just enjoy doing a multi day walk of the 3000's camping at tryfan and nant peris. This way it isn't as daunting and you can travel a lot lighter which preserves even more energy. Never ended up doing it in sections in the end but the plan went something like this:
leave 1 car at the tryfan camp site and use the other to get you to the start, the small lane that climbs up above tyn y groes. Park up here and we have left a car here overnight without problems but perhaps better to retrieve it later.
After dropping off PYOW you can use the first car to retrieve the other car left at the start, drive both to nant peris, leave one and return to tryfan campsite.
After camping overnight you can now do the tryfan/glyder section finishing in nant peris. Use the car there to run round and collect the other from tryfan campsite.
Snowdon summit via crib goch on day 3.
Jesus listen to me, I'll be posting on UKhillwalking before you know it!