You asked

Please provide a copy of the Urban Extents (UE) polygons used in the work described in the natural capital: urban accounts publication released on 8 August 2019.

We said

Natural Capital Accounts for urban areas require the accountant to define both the urban landscape and the green and blue areas associated with it. As part of a project to develop methods for estimating Urban Natural Capital Accounts for the UK Eftec & CEH produced an intuitive, flexible and updatable UK wide method based on existing spatial data. The methodology is detailed here:

The coverage developed by eftec and CEH is currently used in the Office for National Statistics experimental Natural Capital Accounts.

We aim to produce an official geography of urban natural capital areas for wider use. As part of that work the method originally used was examined and it was noted that there is some scope for further development before an official geography is produced. The results of that investigation are detailed here:

The dataset attached is the shapefile currently used in the experimental Natural Capital accounts and developed by eftec and CEH. The current intention is to develop improvements to this coverage to base future publications on. We are releasing this extent under Open Government License with the understanding that it is not an official geography. This dataset is part of an experimental set of statistics and its use by the Office for National Statistics is subject to change. Users are free to use the, "Experimental Urban Extent" under Open Government license.