have you tried myofascial release? I went to a introductory course a few weeks ago and the guy that ran it said he's had excellent results with myofacial release for people with plantar fascitis, might be worth a try? Being a fascial problem after all!
Have a search in your area to see if you can find someone (physio, osteopath, sports massage therapist) that has had myofascial release training.
It's my "new thing" at the moment, it's fab!