Lack of training, lack of base miles, and lack of long runs.
I reckon it's no coincidence that you got up to 8 miles in training, and you also got up to 8 miles in the HM, then by 9 miles things started to hurt. Basically you were underprepared and pretty much an injury waiting to happen. That's not in any way a criticism btw, just a statement of fact. Congratulations on completing your first half in less than ideal circumstances and look at it this way - if you can train more consistently and injury free for your next one, you'll likely smash your PB by a massive amount!
The foot thing could just be down to trainers you're not completely happy with, but sore toes and sole of foot progressing to achilles pain sounds like tight muscles under there - you can ease this off by rolling your feet over a tennis ball (or golf ball if you're a masochist!) and paying particular attention to the tender/tight spots. Good idea to do this for a few minutes every day as it helps keep things loosened off. Also think about investing £20 in a foam roller - they're great for kneading out muscles and getting rid of aches and pains.