There's no magic workout. All of the advice the previous posters gave has to considered within the broader context of the training plan.
You are at 70mpw. That is a good start. How long have you been at this volume? If more than 6 months you could safely increase to 80. And I agree with what was said above; maybe keep that down week a little more respectable at 60ish and once every four weeks.
The bread and butter of 5k/10k training, in my opinion, is threshold training. Have you done a tempo run recently? If you can do 20-40 minute tempos at a good pace, feeling relaxed, then you are in good 5k shape. I won't give you the pace I think you should run these, because the goal on tempo runs is to run controlled and then see what that yields for pace, not race them and retroactively tell yourself it was controlled. It is a good idea to wear a heart rate monitor on these to get objective in addition to subjective data.
Hard, long intervals, ie 5-6x1k at 5k pace, have their place, but that is really only in the peaking phase (last 3-6 weeks before goal race). These workouts are very hard and the temptation is high to race them all out to prove to yourself you're at a fitness level that you might not be. There is a time and place to hammer these sessions, but good volume and threshold training will get you 97% of the way there. Do two to four of these sessions in the final weeks before your objective at 95 percent effort and be honest with yourself about how it feels. You should be able to race a bit faster than you run these intervals because of the adrenaline of competition and the advantage of drafting in a pack.
How is your mile down to 400 speed? This can be very limiting in all track events. It is hard to run 4:48 three times in a row if you can't break 4:25. It is hard to break 4:20 in the mile if you can't break 58 in the 400. Read the "5x60m w/full recovery" thread and think about incorporating that into your training. It might be a good idea to hold off on that until the next cycle though (after you do your 5k time trial I assume).
For mile speed I would suggest 4-10x200 with 90 second rest once a week, and 4-8x100m strides once a week. You can do this after workouts or easy runs. It shouldn't be taxing.
Finally, the long run is important. At 70 mpw I would be doing 16 mile long runs (or 1h45) most weeks. Keep it easy most weeks, but if you feel good you could make it a progression or fartlek occasionally.
Good luck.