Henley was my first full distance (and 2nd tri). Totally agree with you about the fog and nerves. It was a great day though.
Whereabouts in Berkshire are you. I'm in Amersham so depending on where you are may not be that far away. My plan for this Friday is to do a reasonable ride that will take in Henley - partly because I like the route from Henley to home at the end. Usually cycle on my own too because I too have to get the pedalling in when it fits.
I think they're making some small changes to the bike route for Weymouth but hopefully not many changes; it was a pretty good route. There were two hills - one out of Weymouth which wasn't too bad and one up towards a village called Bere Regis (where there had a turnaround point) - that wasn't pleasant. Two laps so did each hill twice. There were some good long, fast, gentle - but quiet road - downhill stretches too.