5G networks envisage to support a range of vertical industries, circumventing any potential barriers from converging various network technologies and administrative domains. Current solutions focus only on provisioning services within single administrative domains. There is also lack of standards for sustainable end-to-end multi-domain solutions that can use existing Network Function Virtualization (NFV) Management and Orchestration (MANO) systems. This is important to enable operators to collaborate and create innovative end-to-end services in a sustainable environment, where stakeholders can benefit without compromises. In this article, we present the 5GUK Exchange (5GUKEx), a novel hierarchical architecture to enable end-to-end orchestration with minimum overhead in complexity and performance while also allowing operators to maintain full control of their infrastructure. 5GUKEx allows operators to use their existing MANO systems for the single domain orchestration and build a multi-domain API based on standardized models exposed by service catalogues to coordinate the end-to-end service orchestration and interconnection. We built a prototype of the 5GUKEx and evaluated its performance through emulations showing that the 5GUKEx introduces minimum overhead. We also discuss the use-cases and trials using 5GUKEx in addition to the experiments focusing on the flexible nature of architecture, allowing us to use 5GUKEx to provide connectivity among multi domains over optical transport network.