Rachel - I agree with 15. What I don't think P&D makes as clear as it might is that Lactate Threshold running counts for much more than its number of miles when compared to a recovery run. Jack Daniels has a formula for this. Too much speed work or racing leads to injuries, well it does for me!
North Runner - I tend to try to use pace, but can't usually get fast enough, so a race can sometimes be better for me. Heart-rate doesn't seem to work for me, nor does "feel". Some Garmins, including mine, can be set up to "beep" if you're outside a defined range.
From an initial read of Jack Daniels' book he seems to recommend treadmills for hill repeats and some types of defined pace runs, though I think even the second edition of his book was written before Garmins etc became so popular.
I'm not starting for a couple of weeks yet, so don't this problem just yet.
mace - Agreed. The schedule calls for the long race-pace tempo run to be 6 weeks before. I think we're stuck. I wonder if there's anything near the tunnel in France!?! I probably will run the Surrey Spitfire since I want to do a 20 mile race anyway, and won't let VMLM prevent me doing everything else.