Being able to say you're proficient or even fluent in a foreign language can do wonders for your personal statement in my opinion. Saying it has no influence at all is wrong.
So why would it help you get into a science based degree rather than any other subject than say, music?
Furthermore, let's not kid ourselves here, having an A level in a language does not make you fluent to the extent that you would be more useful to a business. I'm not saying that languages are rubbish, in fact I think their teaching should be encouraged, but they are not going to increase your chances of success more than any other subject at A level.