I third the tooheys kit, did one a few months ago and have to say i thought it was bath tub water!!. Im not going to waist 3 free brews though, it can be the visitor/ beer scab drink haha.
with the tooheys kits use a coopers brew enhancer and add 500ml of golden syrup leave it in the bottle for 3 months [6 is even better] makes a bloody great thirst quencher on a hot day
give it a go with one of those kits you have nothing to loose and a pretty good beer to drink in summer
i wouldnt be using those pet bottles for long term storage though but im sure plenty of others on here will disagree