So while the card has to be topped up, you need to give us instructions on how to top-up!
Also my suggestion is allow auto-top-up like London transport do with Oyster. If the amount of the card falls below a set value, say £20 then it automatically tops-up, but pulling from my bank say £100 (direct debit maybe?)
Nope I must be stupid. “Use the your card at the top of the statement screen”? I’m really not sure what you mean by this? What statement screen? On an atm?