Relacing the drive belt on a Mowerland self propelled mower?

I have a Mowerland mower with self propulsion and the belt comes off on ocassions, not very often but it happens, I can take it to my local repairer to have it refitted but its £40 a time and my mower's away for a mointh at a time does anyone know how to access the drive pulley under the plastic cover, the one at the blade end is simple