SpreedlyCore is another path to go down. It's a cloud based credit card vault that connects to 40+ payment gateways with a good API and docs. We have PayPal Pro customers who use PayPal for processing but develop against our API. We support GoCardless as well. Due to the fact we vault your cards away from the gateway you can change or add a gateway at anytime. I work for Spreedly who is behind SpreedlyCore.