Maybe this isn't for you if you're doing the work for a customer, but maybe there's some agreement you could come to.
There's a NetSuite partner in Scotland called Eureka. They are also Sage partners. They also have a product like Celigo, that connects systems together.
I'd posit they would have the knowledge and expertise to help you with that, although typically, they'd do the work they may be open to support you in your endeavour.
https://eurekasolutions.co.uk/about-us/
https://eurekasolutions.co.uk/besyncly-integration/
Figure no harm suggesting it.