3 mobile broadband question

Hi folks.

Ive recently got 3 mobile broadband as I was finding it hard to get a good deal with other companies were I live.

Im a little confused as to how much I get out of this 5gb usage cap?. I would also like to start downloading music again as I did before with my old bt broadband. Im concerned that if I go over my usage Im gonna get some nasty charges. I spend about 5 hours a day surfing the net and download about 1 album of say, 10 songs per day.

If anyone knows exactly what you get for your money, I would be happy to hear.

Thanks in advance.....