You just do it. They invoice you in whatever currency suits you both, you pay them. PayPal is, unfortunately, likely to be the easiest way, unless you're willing to hack direct bank transfers or cryptocurrencies. The contractor's taxes are their problem (and thus their decision whether to operate as a company) not yours.

IMHO an intermediate platform is just going to eat into the money without adding value, unless you're using it to find the worker(s) you need. It all boils down to trust: do you trust them to do the work and report progress/time accurately? do they trust you to pay timeously? That's the one point where an intermediary might play a role, but, frankly, if trust is lacking, you don't want to be working together anyway.

DM me if you're looking for very part-time writing/dev work. I'm in ZA, so close-enough timezone to BE.