EssexLion - I've ran 10k on both strategies you've mentioned and would definitely say (as I think just about anyone with any experience would say) that trying to run steady even splits is the best way to get the best out of yourself. If 22 minutes is your PB for 5k, then it's probably fair to say that you shouldn't run the first half of a 10k in 22 minutes. How tired were you at the end of your 5k? Imagine you then have another 5k to go and attempting something close to the same pace!
It's far better to run the first half at a pace your training would suggest you can keep up for a full 10k. It will be a much more enjoyable experience too. The first four times I ran a 10k, I did it off of poor training, yet still tried to go off with the fast guys and then really suffered for it in the latter stages of the race. The last 10k off of decent training earlier this year, I held back at the start and stuck to the pace I was aiming for and as Sarah says - I picked people off throughout the entire race which was much more fun than everyone overtaking me! I knocked 4 minutes off my previous PB!
A sub 20 minute 5k should be do-able by the end of this year if you train.
Not training enough will probably be your downfall though.
I used to be at about 22 minutes towards the end of last year. On the back of nearly 5 months of 10k and half marathon training, I ran a hilly 5k in 20:11 in training last week. I'm pretty confident I'd go under 20 minutes at Parkrun if I ever get myself over there (nearest one is 30 miles away).
If you apply yourself and actually do some training, you'll easily go under 20 minutes in my opinion.
I've never run a Parkrun event before, but as I'm in Liverpool this weekend, I'm considering going along to Princes Park on Saturday morning.
I've always wondered what actually happens with the barcodes. Where does the barcode get scanned? Are there handy scanners at the start and finish lines or something? So it's my responsibilty to scan at the start and finish? Or, well, something else??