How much can I use the internet with Broadband Light 2GB a day?

That is not 2 GB a day but 2 GB a month.

Enough to do your emails for a month and very little else. Any downloading as in the true sense of the word and any video streaming is out.

As an example I would use 2 GB in less than a day and I do very little downloading or streaming.

Depending on what you want to do revolves around what package you need. For the average user you need a minimum of at least 20 GB a month now or an unlimited account.

It's not enough - to do anything at all!

My Kaspersky Internet Security has a network monitor, which records the volume of network traffic by application.

The two biggest culprits are "system" - that will be exclusively windows updates, I think

and "Kaspersky" itself - AV updates...

So whether browsing, social networking, downloading or whatever - the system and KIS downloads would be fairly consistent, I think. That's XP (but let's hazard a guess that Vista or W7 would be unlikely to require less) and KIS 2010 - for the record.

Last month, 10.7Gb of download included 5.3Gb system and 2.7Gb KIS - that's a minimum of 8Gb required to do nothing at all.

3 weeks ago, 1.3Gb usage included 0.5Gb system and 0.4Gb KIS.

2 weeks ago, 3.0Gb usage included 1.8Gb system and 0.6Gb KIS

Last week, 2.5Gb usage included 1.4Gb system and 0.6Gb KIS

Mon-Fri of this week, 1.8Gb usage included 0.7Gb system and 0.6Gb KIS

So, 2Gb would not even cover the KIS upgrades each month - I wouldn't expect other security packages to be significantly different, add in the system upgrades/patches and 10Gb looks like a true minimum for just e-mails!

How to quantify the overhead for whatever else you would want to do?

It would be a guess, and sticking to round numbers - I'd arrive at the same conclusion as sewrobb, 20Gb...

That said, when my son rebuilt a PC at Christmas, and logged into his Steam account, the download of all the games software he had accumulated took us past the 100Gb limit BT applied to our "unlimited" service, triggering a cap to our (alleged) 8Gb service - down to 1Gb for a month!

For subsequent rebuilds he transferred the games from PC to PC (backup & restore).

So, the short answer to the question "How many hours..." is none at all.

O2 is present at my local switch, so they now provide my household's better and cheaper service - I haven't yet tested their unlimited policy though...

68 MB per day (30 days), theres no limit to the amount of time you can spend on the internet, but 2GB is low for a month