I was over 2 hours in HSBC a couple of years ago when I was trying to withdraw money for a car. Even though I had already authorised everything with First Direct and they said they had sent over everything to the branch and all I would need to do is bring ID. Turned out a manager had to authorise the withdrawal and the manager was not there on that day - they also had no authorisation e-mail from First Direct informing them that they had done all the checks. Nightmare
I would assume once Mondo is a full bank, they would have a partnership with the Post Office or someone to allow larger withdrawals of money.
I think £500-£750 is a good amount to be able to withdraw daily from a cash machine. What would be even better was if I was able to set a maximum limit in the app. For example I would normally like my maximum to be £100 a day, just in case someone cloned my card and had my pin the maximum they would be able to withdraw is £100. However if I am making a large purchase that requires cash and I need to withdraw £750, I could go into the app, make the change, withdraw my money from the ATM and then lower the limit back down to my £100 limit.