Please keep the prepaid cards

It’ll be impossible to go overdrawn on the debit cards too, unless you’ve requested an overdraft or it’s due to an offline transaction / delayed payment, which also applies to the prepaid cards.

Monzo will even bounce Direct Debits & stop Standing Orders, if you balance is 0 without charging you. Obviously you’ll have the tools that you need in order to make sure that you set aside enough money for those payments in advance though.