Hi Andy I had exactly this problem with my 2014 Sigma which had less than 2,000mls from new. It is fitted with Girling Type 14 Spitfire/Herald front disk brakes. At slow speeds the pads on one wheel were lifting every revolution of the wheel, as the disk was not quite true. The cure was to fit a brake pad retaining kit (spring steel plate). These are available from Rimmer Bros www.rimmerbros.co.uk . Cost me £16 including delivery. Problem cured. Brian