Newy - Hi I was just flicking thru the RW threads and I found this one. Well during my mara training at the begining of this year I got PF in my left heel. It would be my 4th mara, and whilst building up my lsr's the heel pain became too much after my 1st 20miler at he end of Feb. I did the stretches, and using tennis ball on sole of foot every day, and even had one at my desk at work. But even with those and resting it always came back and couldn't run further than 14m, and only if I took paracetomol before my runs.
I still ran the mara, again dosed up on pain relief, but afterwards decided that as I wasn't running an Autumn mara this year, decided to try and sort it out. I decided to go down the barefoot/forefoot style of running. Starting with just 1-2m to start, and slowly building up. Because most barefoot type shoes are normally 0-4mm drop (heel to toe difference) the calfs and Achilles take a pounding. Also you have to change your whole running style, more upright, higher cadance etc, you feel like you're starting running again. Well I now do all my runs in them, and my lsr's are upto 12m and my speed is upto previous levels, BUT the best bit is no PF pain atall. I bought a pair of Vivobarefoot Ultras which are great, and I'm now after some trail shoes also. I've entered Manchester mara at end of Apr2013, which will be my 1st minimalist mara.
Barefoot/forefoot style running maybe not for everyone, but a relatively cheap option that could cure your PF problem, but it's not a short term fix. You'll need a good 6mnths to slowly build up your runs, in length and pace. Ps I'm 50 so you're not too old to learn new tricks as they say.