The batch (24116 to 24124) was ordered new for long distance routes out of Carlisle, hence the choice of high back seating. With them having high back seating the rear window isn't an emergency exit (they're normally break glass windows) so they have an extra one on the roof instead.
The blue interior lights at the front are to reduce glare on the windscreen for driving on unlit roads at night. Normal lights reflect the bus interior too much and it can obscure driver vision.