Battery & Stop Light + Rear Brakes - Help

Wondering if anyone can help please!

Got a problem with my 200, it's been sitting for about a month, I went to drive it last week and the battery warning light came up with the stop light illuminated. I have since replaced the battery with a brand new one. Same thing happening! Does all this lead to the Alternator? Has anyone had a similar problem?

Also wondering what are the best rear disk + Pad combination to go for? Car is coming up for its MOT and will be wanting rear brakes.

Thanks Guys!
 
I'm having a similar problem as far as the battery low and stop sign appearing whilst driving, you got any more info or had a diagnostics?
i can only assume it's something to do with the charge system