Hi Andy, Just seen your note as I am new to the site. The drive belts on mk 6 Fiestas are 'elastic' ie they have no adjustment built in apart from some give in the belt itself. The fitting of these belts requires the use of several plastic tools (which are supplied as part of the kit with a genuine Ford belt). There is a set procedure for fitting the belt and if this is not followed to the letter the new belt is likely to fail. The process involves rotating the engine in the normal direction of travel whilst using the plastic tools to guide the belt onto the pulleys. No doubt a hasty emchanic may dispense with this method and just lever it in place. The risk is that it may place strain on the waterpump bearings in the process and cause failure of the waterpump - usually sounds like a rumble from that side of the engine. In which case you have to start all over - new waterpump etc.