When's the best time to do the ride? The main criteria were to chose a time that was reasonably warm, so that I could use the minimum of clothing and bedding, and with a good length of daylight.
Mid-summer's day is 21 or 22 June, so that's when there's the most daylight. It's often quite cool in June though, especially at night. I could have left it till August, but by the end of the month, nights are starting to draw in, and if you're outdoors it can become damp in the evening.
In the end, I settled for beginning the ride on Sunday 4 July. I was hoping for a warm July, but as it turned out, there were only two or three days when I could get away with a t-shirt all day. The weather on 7-8 July was "the deepest depression for July on record, centered over Spain" with strong winds and heavy rain. Was the wind going my way? No! And I discovered that northern Scotland can be several degrees cooler than southern England. (There are probably less energetic ways I could have discovered that)
And if I'd done it in August instead, I might not have fared much better. Remember the floods in Boscastle one week, followed by Scotland the next? I might have been caught in both.
They always say that whenever you do it, it will always be the worst weather in living memory for that time of year, so be prepared. With hindsight, I think I would chose late July/early August. Or a warmer sleeping bag.