The group's revenue predominantly arises from the provision of services within the United Kingdom, with less than 1 per cent of external revenue and non-current assets being overseas.

2020
£m
2019
£m
Wholesale water charges784.8767.4
Wholesale wastewater charges939.5905.8
Household retail charges83.886.7
Other51.258.6
1,859.31,818.5

In accordance with IFRS 15, revenue has been disaggregated based on what is recognised in relation to the core services of supplying clean water and the removal and treatment of wastewater. Each of these services is deemed to give rise to a distinct performance obligation under the contract with customers, though following the same pattern of transfer to the customer who simultaneously receives and consumes both of these services over time.

Wholesale water and wastewater charges relate to services provided to household customers and non-household retailers. Household retail charges relate solely to the margin applied to the wholesale amounts charged to residential customers. These wholesale charges and the applicable retail margin are combined in arriving at the total revenues relating to water and wastewater services provided to household customers. No margin is applied to wholesale water and wastewater services provided to non-household retailers.

Other revenues comprise a number of smaller non-core income streams, including those relating to energy generation and export, and those associated with activities, typically performed opposite property developers, which impact the group's capital network assets including diversions works to relocate water and wastewater assets, and activities that facilitate the creation of an authorised connection through which properties can obtain water and wastewater services.