how do I find and relight the pilot light on a Potterton Combi 80 boiler?

My Potterton Combi 80 boiler isn't working for either heating or hot water. When the hot taps are run or the room/rad temperature falls below that set, I can hear the boiler sound as if it is on but the green pilot/ignition light doesn't light at all and there is no heat or hot water. How do I find where the pilot light is located and how do I reignite it? (Of course, i realise that this may not be the problem but it seems the logical place to start given the absence of the green light).