Gemma,
Depending how old your dryer is, it could be that the carbon brushes in you motor are worn down. It's not a difficult job to replace, check out this website giving you advice on domestic appliances with short video guide on how to carry out this procedure.
http://www.apart4u.co.uk/ full of handy tips on all appliances, even shows you a short video on how to repair equipment.
Good Luck
Brian L, April 2010