Mike - I'm not sure why I'm replying, as I share Stevie's view that you will just say "yeah yeah" and carry on doing your own thing.
However, I will give it one more go......
The point of training is to create a stimulus for your body to adapt. This works best in small, tiny, steps. Therefore, training at paces based on your current fitness (rather than what you want to be able to do) is best.
If you want to do an interval session at a pace quicker than your current 5k pace, then IMO you should reduce the distance (maybe to 8 * 400). Alternatively, if you're going to run longer than 5k of quality intervals, do them at your 10k pace - I guarantee if you do them for long enough, they will lead to you improving....
Over and out.
YP