You should receive your bonus upon signing up (and using a referral code.. preferable mine ). Once you have secured £10 worth of credit then you will be able to withdraw and apply to your next phone bill.
I’m with Smarty mobile & I've had £60 paid out to me so far. It goes onto the card that i have registered but I have to hit £20 before it pays out. I registered both mine & my husbands so it builds up faster x