This is the one I got: http://www.amazon.co.uk/gp/product/B002NLOA6O/ref=oss_product
This is the 50w one for 7.99: http://www.amazon.co.uk/50w-Aquarium-Fish-Tank-Heater/dp/B002YEHPVM/ref=sr_1_159?s=kitchen&ie=UTF8&qid=1290472535&sr=1-159
I have some ammonia already, and a test kit somewhere.. as for filter gunk I can get tonnes of the stuff... a mate of mine has a 6ftx4ftx3ft tank with a 1200 litre sump tank!