A few years ago, tubes were absolute crap. Brattons saw the oprtunity and had decent ones made and did well out of it. I think others have since seen the error of their ways and things have improved Never the less, I's like to buy tubes from Brattons but can't. As was explained ina recent thread, they will not sipply anything to Australia now after our idiot government changed the rules and now requires foreign vendors to collect a 10% tax for them. I can't blame Brattons for taking the simple route and simply stop accepting orders from here but that doesn't help me at all.
Many tubes these days are porous, meaning that there is no specific place they leak, the air simply passes through the tube over the whole of its length and width. There is nothing you can do about it other than replace the tube and hope the new one is better (no guarrantee on that, either). The slime mentioned above might work - nothing to lose!