That sounds tough! Its a very long time... CGP does two practice exam papers (for sale) and the AQA does one specimen paper, so thats three ready made past papers. The AQA website also has past papers going back to 2007 with mark schemes, you can make your own past papers up from the "old" GCSE topics. I would split it up into sections and for each one do a re-cap lesson, a revision poster, past paper questions and model answers. Vary the past papers by sometimes doing "open book" tests - in silence but pupils can find the answers in the textbook or revision guide, and normal exam rules tests. Sometimes talk through the papers and give model answers, sometimes give mark schemes out so they can do it themselves either marking their own or someone elses. Mark in red and let them correct in green, so they see where they went wrong and how to put it right. Do a poster race and let them teach the rest of the class in groups. I'm a firm believer that the only way to get good at exam questions is to do exam questions, but they will be coming out of their ears soon enough!