I can't help you with Halifax or AMEX (yet), but my company (https://teller.io/ https://teller.io/) has a Natwest API in production (private beta). If you would

I can't help you with Halifax or AMEX (yet), but my company (https://teller.io/ https://teller.io/) has a Natwest API in production (private beta). If you would like access, please ping me. sg -at- teller.io