Plus one to this. A lot of community membership organisations use it to handle monthly / yearly subscription fees.
Interestingly this is not something that Zapier has, and has caused a number of orgs we know to spin up their own custom code which is silly!
Two core workflows are:
After a form submission, create a paying customer
- Create a customer
- Then save the returned customer ID to your membership database
- Create a customer bank account linked to the customer
- Create a mandate linked to the customer’s bank account
- Create a subscription which schedules payments against the customer’s mandate
- Then save the subscription status to your membership database
Webhook for when things change in GoCardless
This is already achieved by the webhook node 
For example, the customer’s payment status changes and you want to update this data in Action Network so that reminder emails can be sent to them to update their payment details.
Agree with frane that a cherry on top would be to handle the GoCardless webhooks with a bit more finesse - in particular, there is a signature which ought to be programatically verified with one of their libraries.