My girlfriend first received a diagnostic analysis from Tom Hughes at Tri-mechanics - he delivered a talk to the club over a year ago, and a number of Pacers have also since attended.
She has also a visited Coach House Physio who provided ongoing treatment and from further analysis (that agreed with Tri-mechanics) designed the orthotics required - I think they cost approximately 150 quid; the assessment and treatment maybe the same again.
My understanding is that orthotics should be only used as a crutch (temporary) and, once adjusted, you should return to unaided exercise.
Good luck - N