Thanks again for all your input.
I have not tried screwing with my filter, but it is 6 months old and it says the cartidges last for one year - Something to consider though.
I have left wort on a yeast cake for a long time, but the taste appears very quickly and dissipate sover time, so I dont think that is it.
I have tried puling apart the ball valves ont he kettle and cleaning them, but no the solenoid valves and the ball valve on the mash tun. I will citch the solenoids for the next bre wI do on that sysetm and pull down all valves.
Jazzafish - I have just bought two fresh wort kits and two Liquid Malt extract kits. I plan to do one fresh wort kit in an old fermenter that has had a normal sterlising attempt. And do one LME kit through my new 50L kettle and see how they go. If they are ok, I will do a small mash in my mash tun, then transfer it directly to the small kettle and see how that goes. I will not use the solenoid valves for that, and I will clean out all ball valves beforehand.
I took a sample to Grain and Grape today and got then to taste it. They say it is not Brett, and tastes quite astringent and not barnyard like at all. After the dicussion I think I have had brett to begin with and the problem has slowly changed into something else. The original ESB I did was heavily 'barnyard', that I am sure of, a few people tasted it and all agreed. Thne I think perhaps I may have done a couple more that had some brett, but with decreasing amount due to my sterilising regime that I slowly introduced - which makes sense as I cant see how I could be getting bacteria into the brews at the moment. They suggested perhaps mashing to high or over sparging. I am fairly sure that hasnt happened. I have a temp readout on the mash, the highest I have ever seen in during the sparge is 77.5C, and it is usually more like 74-75C. Having said that, it is a big mash, and could be hotter in some places than others, I wouldnt be surprised if some parts got up to about 79-80 in some cases, but probably not in all the batches that have exhibited this flavour. Could temps this high cause bad flavours?
Warren - DMS smells kind of like eggs or farts? If so, then defintely not. I heat the boil with the lid on, them remove it when it starts boiling.
Beernut - I definatley agree that sanitising my garage is a good plan, but I would be surprised if that was whats causing my flavour problems.
Crozdog - The guys at Grain and Grape didnt think the problem was that bad. It tastes awful to me, but inpart due to the fact that it is very bitter. I have always preferred a slightly less bitter brew. It isnt just the bitterness though, its also a bad taste that goes with it which they described as astringent, which I agree with. Some of the brews I have done have been tasted by mates, one in particular is a brewing buddy and everytimes except once he agreed there was a problem. A lot of my other freinds, who dont know much about beer dont seem to mind it at times, but I am unsure if some of them are just being polite....its usually my brothers who are the most honest and willing to tell me my beer is shit when it is - so its kind of hard to guage how much of what I taste is what John at Grain and Grape described as 'Cellar Palate'.
Reviled - I am very paranoid about this type of thing. I have brewed in the past many batches that would stand up to commercial beers. Now every batch sucks and despite the fact that some of them are just drinkable, they are still not good enough in my eyes - not to mention tipping out hundreds of litres of beer which is just way to gruesome to drink. I not only want to be able to brew great beer, but I really want to know what I have done (or not done) that has cause this to happen to increase my understanding of the process and practicle brewing knowledge.
I will run some experiments over the next week or so and get back to you guys with the results. any more ideas are more than welcome.