It is more difficult than you describe it. To set up a monthly payment the bank verifies the request (e.g. if you sign such direct debit for the gym or your electricity bill). Every ebamli I ever used has a page with all these direct debit setups and alerts you when a new one is made to bring your attention to it. These also have limits. And a decent bank would scrutinize the direct debit. A gym or Vodafone will fly easier than a direct debit to VodkaPotatoLimited in Russia or China (no offense) when you live in the UK.

As to prevent the overdraft, just ask the bank to NOT have overdraft capacity on your account(s).