Thanks for all your advice. I was mulling it over and was going to sign up for the 5K this afternoon but first I wanted to run this course and see how I felt afterward.
Well this morning I set off all rugged up on a cold and windy day, the rain spiting intermittently. There are a couple of long gradual hills on this course but I was running them at pace nevertheless still breathing normally.
Coming into the end of 5K and feeling so good, I decided to do it again. Even though I was running on sore legs, with no carbs, to speak of the last couple of days, I still managed the 10K in just over 38 mins.
After that effort, and feeling like I could have done another 10K I went to the post office and paid for the 10K. While I maybe making a mistake I think that my training and diet have enabled me to jump a level and I just have to take advantage of it. With my current level of fitness, I reckon I can run a 10K PB and still not overdo it for the marathon the week after.
As you guys are always saying, we are an experiment of one, and I do have to try a few things to see how I react. One thing is for sure, like Rob said, I would have sprinted that 5K and could very well of hurt myself.
Anyway, don't get me wrong I, unlike my wife, don't ask for advice, like she does mine, simply thinking that doing the opposite is a sure way to success ;)