I had an achilles problem and it dragged on a while. Probably caused by old shoes.It's odd as it's only in one foot and could be other factors too but I'll keep an eye on it and do some strength training.
I should (and usually am) quite supple due to doing yoga twice a week (and pilates).
Good luck with those trainers. They're a lovely looking shoe.
Massage of the tendon (up and down and also rolling it in fingers) to break down any scar tissue really helped. To start with the tendon felt like bubble wrap!
Avoid running up hills as that puts a lot more strain on it & warm up slowly.
Good luck.