It doesn't *quite* work that way, you don't have a fixed 2G peak quota and a fixed 100G off-peak one. If you use less in peak time, you get a lot more off-peak (so you could currently use 1G peak and 150G off-peak with that number of units).
If you are on a 20CN line then nothing changes anyway.
If you are on a 21CN line (including FTTC) then peak time will start calling off units at 1==2.5Gb instead of 1=2Gb and off-peak will go from 100Gb/unit to 50Gb/unit. It isn't a straight 2.5G+50G though - if you only use 1.0G during week-day days in the month you'll have 1.6 units to use off-peak (80Gb if all used in "normal" off-peak, more if some is used on the over-night cheaper period which is staying at 1000G/unit).
Login to clueless and check the details for you use pattern this month and last couple, that will help you deduce if the change is going to affect you significantly. I have three units now and might need to push that up to four (moving a couple of scheduled transfers into the overnight cheap period means I won't need to go further than that). If you do want to move and are in a fixed contract period, you may want to decide quickly as they are currently waiving early exit fees for people leaving due to the pricing changes.
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Current ISP: Andrews & Arnold (AAISP, aa.net.uk) via FTTC at ~36Mbit down & ~10Mbit up, joined July 2011.
Previous setup: Be Pro with UploadPlus (ADSL2+, AnnexM), 12ish Mbit down, 1.6 up, happy customer for ~2.5 years.
Edited by dspillett (Wed 26-Oct-11 13:32:25)