I've never raced a 5K (we only have two every year, one is on track, the other is part of a 4 man relay and I've never got round to them) but my 10K is 36:53. The 5Ks that I've done in training are all 10K race pace time trials, but my best was 18:10 when I was a few seconds faster each mile than I needed to be. I'd like to think that I could shave at least 30 seconds off this in a race.
As for my training, the intervals don't stress like a real race. I'd go so far as to say the 800s at 10K race pace are quite easy because you have a 1:30 break every rep, plus you're only doing 5 miles equivalent. Its a great way of getting the body used to the pace without leaving you out of breath.
The time trials are tough though!!! But I only do one a piece in the final fortnight before race day.
How fast do you do your 10 mile weekly runs?