In response to your question about Kent marine salt Aaron, I am about halfway through a bucket because like you i got a good deal on it of £40 for 25kg's. I don't have that much experience with different salts but i wont bother with another bucket. My first salt was red sea pro which i found very good, but since using the kent i seem to get more algae on the glass. This of course could be completely unrelated but it coincides with constantly low alk and calcium which i now have to supplement.
This is just my opinion and based in no fact at all and the low alk/calcium may be that the tank is older with more stuff using it up but for whatever reason i will go back to the red sea next.