Running in 4 y-old shoes (assuming you've been using them for 4 years) was asking for trouble. I'm sure you already know this. So why ask questions here when you already knew:
a) what probably caused it, and
b) what to do about it?
I believe the Edinburgh course was fairly hilly? Referred issues from your Achilles could be a factor. Do you stretch that area? It's unlikely to be PF, but I'd start incorporating PF-specific stretches into my warmup were I you, just in case.
New shoes, a three-to-five day course of your favourite anti-inflammatory, and a nice set of stretching exercises for a week should see you back on the road. Good luck.
Oh, and practice asking smarter questions… 🙂