I think the Always On goodybag needs a slight change to it. Rather than give you unlimited data overnight only once your 40GB has run out, the off-peak data should never count towards your 40GB.
I think you'd get a lot more even spread of data usage this way, as currently you need to be very protective of your 40GB, as the 'slowed down' data rate is far too slow for many modern uses and is impractical to use during the day.
With the change, it'd be simple to spread out the 40GB of peak use during the month and then off-peak could still be used overnight, without fear of compromising my daytime experience after only a few weeks of usage.
I came up with this after experiencing repeated difficulties with using the 'slowed down' data during the daytime. I get webpages that time out, Apps that won't log on and other such issues, but no issues overnight when scheduling updates for my apps etc.
I've only been with giffgaff a few weeks and love so many things about it, but this is the one thing that's ******* me right now and making me want to switch to a properly unlimited data plan with one of your competitors.