Hi BritNick,
Thanks for the advice, that goes for everyone else who's taken the trouble to offer comments and advice!
When you say "but don't forget to get to Cray in daylight before grouping" what does that actually translate into on the day? Does the time differ or do the organisers work on official sunrise, sunset times? If we get there before grouping what does that mean? presumably we can just crack on as a pair?
What sort of time schedule gets you to Cray before grouping?