Hi, just wondering if my brake fluid is running low, would I have to take the car to the garage or could I just buy the fluid and top it up myself? I know I can go and buy it, but owner's manual gives 2 options for the correct brake fluid. Can I just use any of them? Or do I need to find out what is in the reservoir already? 

As long as you get a decent brand for your car it will be fine to buy it yourself. 

Unless you have a leak which is unlikely on a car a few years old I wouldn't top up the fluid, this is because the reservoir is designed to hold enough to allow for the thinning of the pads which means more fluid is held in the calliper behind the Pistons so as the level drops its actually a good guide to your brake wear, when you fit new pads the fluid should rise back to max level if pushed back or topped up to max if bleed off as it should be on modern cars