go and see a good physio. they will pick up any muscle imbalance, knee mistracking or any other issues very quickly. i wouldn't rely on a bike fitter to do this.
i had a similar issue to Branwen. all sorted by a visit to crystal palace sports injury clinic (physios) and a specialized body geometry fit session and footbeds.
This was my experience too - go and see a physio then get your shoe and pedal set up checked by someone who knows what they are doing (which includes scherrit).
This was my experience too - go and see a physio then get your shoe and pedal set up checked by someone who knows what they are doing (which includes scherrit).