5GB of Bandwidth?! Yikes! I've downloaded 7GB+ worth of xbox demos this weekend alone! I can't imagine surviving on 5GB. I guess you make use of what you have, right?
Anyways, your internet service providers approach to changing your plan is unlike anything we have in Canada. For us, once you reach your bandwidth limit, you'll be charged extra per GB. Obviously, the higher your internet plan the cheaper the over charge fee is.
In terms of monitoring software, ours worked on a daily basis but there was no way of switching it over to the next month or stacking bandwidth amounts...so I wouldn't worry.
So what happens once next month arrives? Do you stay on broadband or do you go back to being on dial up? Sometimes it also depends on your billing cycle. Are you billed from the first to the 30th of each month? Or is it something different?
Dude, it's horrible. It's only for about half the year, the rest of the time I'm flatting, with 30 gig. Our 5 gig is shared between 3 people, too

As for being charged per GB, we do have that option as well, but for my mum it's cheaper to go onto dial up once the limit's been exceeded, because she doesn't pay extra for that.
Once the new month arrives, we just get a whole new 5 gig block of broadband to use up. Just starts again. According to the website, we're billed from the first to the last day on the month. I'm just confused, because it's not the first yet but we're back on broadband speeds when we should still be on dial-up until tomorrow.
I'm just going ahead and downloading. I figure, since our usage meter is telling us we aren't back on broadband, their fault for being misleading.