littlered,
Hope your heel pain would have settled by now. Perhaps you should tackle this from your running. As a runner, I can recommend you to try some interval work to boost your speed rather than running long hill intervals. Hills make you stronger but speed comes from the turn over or cadence of your legs. In light of you heel probom, unloading the calf and the achilles tendon from long hill effort would have been a good strategy to settle your heel pain. Some ideas to boost your speed are fartleks, tempo runs, yasso 800 and the good old 800m intervals x ?. good luck with running.