Thanks for that.
As I said, I only noticed the soreness after I started wearing the knee support. You said that you had issues until you stopped tying your shoelaces tightly - could it be that I've been doing the knee support up too tight?
Thanks for the advice about hills as well - generally when going down, I relax and let gravity do the work. The first time I noticed the achillies soreness, I did attempt a faster run up a hill - maybe that combined with not being used to the knee support caused a bit of an issue?
As to my profile, I've been forgetting to update that - so it's well out of date. My shoes aren't old though, and I have a newer pair that I rotate them with. Both pairs are Asics Gel 1160; the only difference is the colour.
Interesting point about the route, I'd never thought of that. 
If the soreness doesn't clear up, or I keep noticing it during runs, then I'll go to the physio again - but I'm not going to do any running this week, and then stick to 5k for a while. Annoying though - I thought I'd just cleared up one problem, and then another one pops up.
As you stated, I'm not an absolute beginner, but because of the knee problem I had to have a long break, during which I had physio etc, so I'm only just working my way back up to 10k now (before the knee problem, my best was 15k). Still, to be safe, I'll stick to 5k for a while and do my less hilly routes as well. 
Edited: 22/11/2012 at 14:30