Layer Estimates:

Layer: B1 Mastermap Text (ID:0)
Count: 711
Extent:

XMin: -356360.575505404
YMin: 7543745.19389726
XMax: -352413.380467516
YMax: 7545485.83901687
Spatial Reference: 102100 (3857)

Layer: B1 Mastermap (ID:1)
Count: 4864
Extent:

XMin: -356417.454454694
YMin: 7543704.94461954
XMax: -352365.460093813
YMax: 7545489.42580126
Spatial Reference: 102100 (3857)