Hi Steve, yes its more than likely the brushes (carbons). The brushes (2) fit either side of  the motor new brushes are about 4 cm long (duff ones can wear down to 1cm)  u can buy them for around £5. To remove and fit them I would go to youtube, rather than me writing a whole paragraph. They are fairly simple to fit and it would save you around £40-£60 in engineers charges. 
Jeff G
                
 Jeff G
                
 June 2011