Buy using a ‘non bank’ for transactions, will this be bad for credit scores?
A bank doesn’t report normal transactions anyway so minimal impact. A credit report is based on credit rather then transactions.
Banks usually report things like going over agreed limits (including going beyond zero if you have no agreed limit), time spent in a overdraft (authorised and unauthorised), along with the amount you are over any limit and how long for based on a continuous monthly snapshot. Plus the time you’ve held the account
There is something to be said for having some history with a bank and your behaviour, so if Mondo was your only account potentially it would be a little detrimental but probably not by much.