In British grammar 'different from' is correct. I was always taught this as a mnemonic: 'Different from' because if something is unlike something else it is repelled away from it, but 'similar to' because if something is like something else it gravitates towards it. And 'different than' i just plain incorrect; idiomatic, but grammatically incorrect.
Unfortunately language doesn't always follow such tidy logic. All of the reference grammars I have checked disagree; "different than" is as grammatically correct as "different to" and "different from" but is simply out of fashion in the UK. So we get a situation that's very common: there's a version that is decidedly safe because it's accepted by pretty much everybody ("different from"), but people are not wrong if they use one of the other forms.
You only use 'than' with a comparative - stronger than, faster than, more expensive than - different is not a comparative. You can only follow different with 'than' when you are introducing a clause, i.e. The stream followed a different course than the map showed. But then, as you will see, it does not directly follow it.
You're free to write like that if you want to, and your writing won't be wrong because of it. But as I say, all of my reference grammars say that "than" is ok too. As indeed it should be from your logic, because "different" is a comparative! (To be precise it's a non-gradable comparative adjective).
