Actual on-station signage will mostly be from a set of standard parts from railway suppliers. https://wiki.openraildata.com/ https://wiki.openraildata.com/ has

Actual on-station signage will mostly be from a set of standard parts from railway suppliers. https://wiki.openraildata.com/ https://wiki.openraildata.com/ has information about various open data feeds available for the railways in Great Britain, and https://tfl.gov.uk/info-for/open-data-users/ https://tfl.gov.uk/info-for/open-data-users/ for TfL. Third party solutions for things like railway adjacent bars presumably use one of these to get departures board info etc.