Multivendor shipping by postcode/city/country

Hello, I run a multi-vendor marketplace and different vendors offer different shipping. My main issue is that when, for example, Vendor A ships to both UK and USA and Vendor B ships only to UK, if they are both in the cart together the customer is able to order both to the USA. The site basically disregards/overrides the shipping zone restrictions of Vendor B.

I have found a plugin to work around this on the country level, but I’d now like to add some vendors that only ship to certain postcodes in London. Could anyone suggest an efficient way to do this, without allowing their products to be accidentally ordered by customers elsewhere?

Also, if you have a basic solution for the original problem on country level, please let me know too. Thank you.

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