Best literature to learn BSL (British Sign Language) with?

Hi,
I’m a nurse in the Uk and would very much like to learn BSL (British Sign Language). I have bought 3 books so far which contain words, phrases and photos; but find that although all the books are BSL based, they clash. It appears that that all contain different variations of the same phrases or words.

Is there any books out there that will teach me one standard way for everything? Just until I am confident enough with the language to learn variations?

Thanks alot
xx
.