I'd stay just friends mate, from my own experience trying to be more than friends with a friend can totally fuck it up, then your end up not even talking at all. You don't want this do you?

Never go out with a best friend.

Like they alll said before me, never go out with a best friend. Speaking from experience, it ruins friendships. You might both go in saying "If it doesn't work out, We'll be great friends still", but in reality once you cross the more than friends line, nothing will be the same. Honestly, it's your decision but if you don't want to jeopardize your relationship, I would wait until someone else comes along. If you do notice her becoming increasingly flirtatious, than you'll have to make atough decision. But remember, you will only ever have one best friend like her in your life. There Are Plenty Of Fish In The See, a famous quote. You will always find someone else in your life. Why ruin what you have?
~Good Luck :]

I personally think that if you think you have a chance then go for it, Later on you'll think about how you didn't get the chance to be with the girl later on. It's good that you have a great friendship it's something you can fall back on if it doesn't work out. You may ask for our advice but when it call comes down to wanting to do it or not it's up to you.

Anytime, feel free to message me whenever if you ever need to talk about anything, alright?

Yes, flirt with her, compliment her, but don't do it too much.....makes you look desperate. Once she know you like her, you're halfway there!