Firstly, big thanks to everyone who took the trouble to reply. It means a lot to get some different viewpoints.
This morning I completed step 1 - my first ever parkrun. It was OK. Just OK. Not the wonderful experience I hoped for. Of the 316 runners plus volunteers a grand total of 1 spoke to me, and that was the lady doing the newcomers' briefing to ask me if I had parkrunned anywhere else. All attempts at conversation with fellow runners before the start about trivia failed. Surely not everyone is in the zone?
After the cattle stampede at the start things thinned out after about 1-2 km and I was able to run "properly" without tripping over others. Over the line, job done.
As for a 10k race next, I'm not sure I will bother. Instead I will see what sort of a plan My Asics suggests and examine it in minute detail for the next few days.
I won't see my running friend until Thursday so that gives me a few more days to procrastinate!
PS I took an Imodium just in case...It worked so no need for the change of clothes and wet wipes.