The figures use historical data from UK Parliament web site
http://www.data.parliament.uk/dataset/elections
The final data point for 2019 is the result projected by the YouGov multilevel regression and post stratification model published on 28 November 2019.
https://yougov.co.uk/uk-general-election-2019/
Note that the “other” category in most cases is dominated by UKIP votes, but also includes the Green vote. The historical data set does not include details. As the Brexit party is not standing locally the Other category for the 2019 You Gov projection can be assumed to be Green.