Did you really mean an instant "buy a goodybag" button?
Many new members are buying topups and forgetting to buy the goodybag afterwards, and/or losing a few pence of credit because the phone has used some data before they bought the goodybag from it. This is often caused by not understanding that the topup option is not the best way to buy a goodybag. Hence the need for https://labs.giffgaff.com/idea/16712751/encourage-users-to-buy-goodybags-without-adding-credit-first
But if that's what you mean, how would it differ from https://giffgaff.com/buy/goodybag -- especially considering that the paypal option on the second screen would already be selected if that's your default payment method?
Sounds good to me.
For me I would like to see a fresh new feel to the app. Something that's functional, logical and makes me come back. As a new user. I joined, got the app, had a look around and then put it down without thinking any more of it.
Appreciate that there are lots of great qualities that the current app brings but it would be nice to bring this up to speed whilst making use of the awesome technology phones can provide.
Maybe you could introduce games into the app for fun and competition to keep people engaged. Maybe some challenges and badge rewards. For example, provide 5 pieces of help and get a badge along with payback. Get 10 kudos and get a reward badge plus payback. Things like that have been amazingly successful with the likes of xbox giving a sense of achievement.
On another note I would like to see the forums revamped. It might be me but I find it a pain to navigate back to a tread I was on to continue to read it. Simple easy and quick is key.
Why not introduce phone support guides. Dedicated page that allows a user to pick their phone and read up on where things are and what things go in their phone all published by users. To then confirm posts maybe some kind of verification that rates how successful a piece of advice is.
Hope this helps