Mark, I shall be there. 8.30 might be a tad early, but the weather's been good and attendances have been on the high side, so it's as well to get a parking space early if that's how you're coming. I'm sure Liam wouldn't mind announcing you, if only for the novelty value of your challenge, but if you're neither here nor there about it it's not a big deal. Stick around for a coffee if you have time. Beware: two Peter Collinses run this parkrun - I'm the older, slower one.
I tend to agree with tasty snacks. Just take a look at a big race on the track and note the huge variety of styles even among the fastest runners on the planet. Look at old videos of Paula Radcliffe and marvel at how awkward she looks, even as she's setting world records for the marathon. Yes, changing your style might make you faster, but be prepared to go slower at first, and then never get faster anyway, or to suffer injury of some nature if you're unlucky.