@Barkas I think you've got the wrong picture, though I'm not sure quite where it has gone wrong! If your initial bundle has expired, you have opted in to the most appropriate Freebie for your purposes, and have had confirmation, or seen on your online account that the opt-in has taken effect, then, when you top up by £10, that £10 is added to your credit, and you get the 30-day allowance of UK minutes, UK texts or UK data appropriate to that Freebie - only one of them, not all three! You did see the Freebies tab on the Tariff link that @BandOfBrothers gave you?
So you don't actually "buy" the Freebie, you get a "bonus" (for lack of a better term) for topping up. If it's the Freebie Minutes, for example, you'd get 150 UK minutes which you can use during the first 30 days. But any minutes above this, any texts, and any data, would all be paid for out of your £10 credit balance. Any funds left in your balance just get moved on, and provided you make chargeable use of your phone at regular intervals (see the PAYG Ts&Cs), they'll just keep going until you've used them.
But, if you want a further 30-day allowance of whichever element you want, you have to top up again - and again the £10 gets added to your balance!
