Just to be clear, the plan so far is that Monzo won’t charge fees for it’s standard services.
The only* things that you will pay fees for are the overdrafts & possibly, expedited delivery for the debit cards but only if you choose to use those services.
*There is also a potential fee for ‘investigations’ in the T’s & C’s but that’s charged:
to cover costs of investigating suspicious transactions at customer’s request (we may, at our discretion, waive this fee if genuine fraudulent activity)