Monthly transfer allowances

[byff]

I've got an unlimited broadband connection, but for the same price, I can get sky's package that gives me broadband, free phone and the basic sky TV.

Only trouble is, the sky package is capped to 40Gb/month.

Is there anyway I can find out what sort of usage I've had in the past or is that something only my ISP can provide me.

BTW, if you can rough guess it, three desktops and a laptop. 1 desktop gets used for p-2-p file sharing for songs and msn, 1 desktop gets used for online games and the other desktop gets used for surfing PH and porno vid d/l's. The lappy gets used for surfing only mainly, no d/l's of any noticable size.