This grid square really is dominated by the power station. The paths around its perimeter mean that you can see quite a lot of its various bits and pieces (without having to go on a "site visit"). I've found a fairly detailed diagram of the power station
here (pdf file), but since big companies are liable to regularly re-organise their websites just do a search for 'Fawley power station' and you'll find it soon enough. Only a few parts are labelled, but its cutaway style means you can make sense of the different buildings.