Shopify uses Stripe for its Shopify Payments option. Stripe requires either a SSN (only available if you reside in the USA), or an ITIN number (quite a process to obtain) for Non-US citizens/residents. This is my understanding, so please do your own research into this. Please share here if you find anything different. Thank you.
We're a UK business looking to achieve everything you've listed in your post? Could I by any chance pick your brain on how you solved this issue. It would be a huge huge help as we've hit a bit of a road block!