Now that I've had a day to recover, a couple of points that may make the lives of others easier:
- The B2B at OTP was really a breeze - on the B2B thread navylad had a problem not so long ago, but I found it fine.
- On the return leg I couldn't get AA to check my bag from PHX - JFK - LHR - HEL - LHR - OTP as it passed through LHR twice in one day. They said that if they checked it to the first LHR stop then I could pick it up from the AA luggage desk when I arrived back to LHR for the second time. I was very sceptical, but it worked absolutely fine.
- I, like many people, stayed in Vienna House. I tried calling when I arrived to get the shuttle bus but couldn't get through, so decided to walk. I wouldn't say that it was terribly well lit, had many people around, or the smoothest pavement, but I got there in a bit over 10 minutes. Just make sure that you go to the carpark straight ahead of the terminal, get the lift down two floors, and then keep walking in the same direction towards the main road (using the footbridge of course!). The shuttle bus the next morning took almost as long as it seems to take a very convoluted back-road route.
Good luck to everyone, and I "look forward" to doing it all again in July (maybe 32 hours from leaving one hotel to arriving at the next, with 5 flights in between, was a little too much!).