Yep mate the uni knot is a winner... Also called a lot of other names etc but this is how it is tied:
http://www.marinews.com/Uni-Knot-361.php
Anyway I have used this knot a lot and I can't recall one time yet where it has ever failed. The line usually breaks elsewhere from heavy fish on too light a line then at the knot. The trick is not to cut the extra off too close to the knot, because as tension is applied to the hook on a bite or frun of a fish, it tightens the knot a little more drawing in that little tab of extra line, and if too short, the knot will release, so keep a good 3-4mm of extra hanging off the knot. Make about 4-5 wraps on the line when tying the knot too.