You will need to get your Starling Developer id to be able to connect to the Starling Bank APIs. This is in a read only state.
Optionally you can also provide an IFTTT Webhooks id which can be the trigger for an IFTTT applet.
Put this PHP script on a server, add the config id's, decide if you want to have JSON or RSS output (none needed if you're just going to make the Webhooks call).
Then setup a cronjob to trigger your page on the 1st of the month.