Steve - in fact it is even worse than that. I always do the full 26.2 in training once before London. So, yes you've guessed it, I have done the track session the day after my 26.2 training run. Felt a bit creaky at the start but was fine when I got into it!!!
Thomas - great session and further confirmation, if any were needed, that you are nearer to a 2:45 marathon than a 3:00.
I did these Yassoo 800s during my training for my first sub 3. I had to give it everything just to keep them a couple of seconds under the 3 mins. So I reckon they are a pretty good predictor as I had to give the marathon everything to get a couple of minutes under the 3. I guess the only thing in my favour was that the track sessions were on a Monday and as I always did my long runs on a Sunday I was doing them on tired legs, so possibly could have been a little faster.