"Staged Broadband"?

[#1]

With my Mobile Phone, I'm with giffgaff.  To be honest - if it wasn't that you have to pay line rental to someone to have broadband - I could possibly get away with using them for everything. 
Never mind.
One thing they do is give you graded options for the service you want each month.  You buy these - as with other mobile providers as an "add on" to your service.  In the case of giffgaff, they're known as "Goodybags". The number of minutes, the amount of Data you want to use for surfing the net etc & how many texts.  Something we're probably all familiar with in one form or another.  Theirs go up in £5, £10, £12, £15 and £20 a month.  It does make me wonder how nice it would be if you could choose (aside from the Top Up Service that Plusnet offer when it looks like you're running out of GB in any one month) "Top Ups" on the Plusnet Broadband Service in incremental stages - 10GB - 15GB - 20GB etc instead of just having the choice of the Essentials or the Unlimited Service and nothing else?
Would it be useful to have that flexibility?  What do folk think?

[#2]

Hi,
Used to have that years ago - it was called "Broadband Your Way" - up to XMbps plus usage requirement.  As time moved on, one got more for your money with Vaule then essentials.
Now that unlimited is £3.49 per month you can't get much more for much less!

[#3]

Hmm. Looks good - but works out the same in the end! 3 guesses that Line rental will go up when my current contract ends to £15.95 too! 

[#4]

If it does re negotiate or leave.
Or get something like 3 with tethering because if you are tethering on GG's £12 bag you are in breach of their terms anyway.

[#5]

Peculiarly, last time I looked - you can now tether with the £10 goodybag. Yet that now has the 1GB limit on!