OK,
So assuming giffgaff don't want to/can't :
Offer a second £5 "Unlimited" Data Goody Bag
Either because two £5 Goody Bags is confusing (pull the other one 
).
or perhaps it just discourages people going for the £10 Goody Bag.
or perhaps because offering a £5 Goody Bag with less that 1GB allowance results in everyone complaining 3 give you more...
Offer 1p per MB data
Presumably because it costs giffgaff too much (unless you commit to a minimum spend, since £10 unlimited is OK).
It just isn't worth having a customer that spends 25p a month. I can understand that.
Allow you to have more than 1 Goody Bag active at a time (30 days at a time)
For technical complexity etc. I assume.
So why not offer a £2.50 for 100MB then 1p/MB Goody Bag
This gets giffgaff past the 1p per MB results in some customers with 25p per month spend and hopefully covers the minimum spend cost to allow 1p/MB in the same way giffgaff can offer unlimited for £10 spenders.
If cost of £2.50 transaction processing is too high, then only allow it from existing credit. Surprised giffgaff don't do that for £5 Goody Bag already.
Very, very, very Light Data users can carry on with current 50 per day.
Yes you can make (virtually)everyone happy all of the time
