Hi, I'm a 20 flat at best 5k runner who does have some basic speed (sub 60 400 now, was faster before I had back and knee trouble). It does not seem help me run a decent 5k, but that does not mean that if I improved my speed, that it would not improve my 5k.
It would depend on why my basic speed improved. If I became more explosive, such that I could dunk a basketball or pull off a decent long jump, that would improve my 200, but not my 5k. If I learned to run more efficiently though, this would improve both. Sorry if this is too obvious. I think this why sometimes improving one's 200 will lead to a fast 5k, but other times it will not.
I think 200 meters reps will improve the latter. A 200 meter race may be about explosiveness, but running 200s for reps is more about efficiency and speed endurance. 300 meters might be a better rep distance though, because that's when most people start to slow down.
Oddly enough, I just went on a 1:50 run. It was only a little over 11 miles, but it was over rolling hills. I don't normally do this, just decided to the other day. I haven't read the entire thread yet, so I'll take a close look at the training.
I'm only at about 25 miles per week now. I want to keep my weight up. Just setting goals in the 5k to test my cardio for general health, and to run a faster 800/mile. Maybe we can compare notes on training though. I'd also like to run under 19 in the 5k, because that would break my old PR.