There’s no cost associated with having unused credit: I have… at least £30,000 available across a few different cards and I use probably 5% of that at most and my credit rating is great. As Paul said, history is what matters, responsible use of credit is key and access to a lot of unused credit shows responsible behaviour because an irresponsible person would spend up to their limit.
That said, personally I do not use a debit card ever. I spend only on a credit card – which is paid off in full every month – because debit cards provide direct access to your money and your bank cares a lot less about your money than they care about theirs.
If your debit card is stolen and the thief drains your account, you can contact your bank and report the transactions as fraudulent and they’ll investigate… and until the investigation is complete, your account is empty… and that can take weeks. Look around this forum for tales of people having fraudulent transactions empty their accounts and then being unable to pay rent because they have to wait days/weeks for an investigation to complete before the money is returned.
If your credit card is stolen and the thief uses every penny of your available balance, you can contact your bank and they’ll immediately freeze those transactions and investigate so they can recover their money – which matters a lot more than your money. The moment the transactions are frozen your balance is back and you can continue your life as normal, the fraud has no impact on your life.
A credit card has transactions whereas a bank account has money. When you make a payment with a credit card, you’re spending the banks money, when you make a payment with a debit card you’re spending your money.
Although you can work around the debit card issue by having multiple bank accounts, each containing enough money for you to live if the other is compromised, it’s a lot of overhead that just isn’t worth it when you can use a credit card instead.
The only situation in which I’d recommend against a credit card is for someone who has trouble controlling their spending and needs the safety net that spending from a bank account with no credit facility provides. For someone in that situation the risk of using credit irresponsibly is far higher than the risk of an account being compromised.
Monzo is my primary bank account, I use it for all direct debits and standing orders, but my Monzo debit card is permanently frozen and I have never used it, and I never will use it, because that provides direct access to my bank account and that’s a risk that it is pointless to take. A credit card does everything a debit card does, and has greater protections and provides rewards…