Hi @kev,
Welcome to the community 
The current version of @openzeppelin/contracts-ethereum-package is 2.4, which is the upgradeable equivalent of OpenZeppelin Contracts 2.4
We are working on removing the need for @openzeppelin/contracts-ethereum-package, see the Roadmap for February - March 2020
In the meantime I will see what I can find about a 2.5 release of @openzeppelin/contracts-ethereum-package.