This may have helped.....
OSI Geospatial Signs UK Navy Submarine WECDIS Software Supply Contract - ASDNews
"OSI Geospatial's software was chosen for the UK Royal Navy's most advanced nuclear attack submarine after critical analysis determined that the unique features of ECPINS(R) W (Sub) provide the submariner with a clear tactical advantage in both open ocean
as well as the complex littoral battlespace."
...not sure they are as cheap as £1Bn each....