After 2 weeks of misery complaining about the 'Plantar Fasciitis' that had struck me down, I actually went to see someone who knew what they were talking about yesterday.
Turns out it's not PF at all ( ), I merely have a dodgy left foot that 'corkscrew twists' through 12 degrees from back to front as well as ankle stability problems so, when I run all the pressure is going directly through the fifth metatarsal and causing injury.
So, 120 quid later, I am on the road to recovery, I think, and instead of being out for many months, a few weeks should see it sorted...
The moral of all this is - don't try and self-diagnose - see an expert, recommended by people you trust and get a proper diagnosis and some proper treatment.
MH