If it's been bothering you for years, go somewhere serious and get it dealt with. My suggestion would be Roehampton Uni: http://www.roehampton.ac.uk/sport-roehampton/performance-centre/other-services/index.html
Also:
http://www.londonpodiatry.com/ (very expensive, but great reputation)
In Ealing:
http://www.sportandfootworks.co.uk/ (cheaper than the above two, were recommended to me - you want Joanne)