Graham Harrison wrote:

What, with sufficient space for bikes, prams and kitchen sinks
(otherwise known as a *guards van*)? My understanding was
Electrostars optimised for passengers (longitudinal seats - lots of
standing room).

The class 378s are supposed to be class 376-derivatives. Those suburban
Electrostars have limited 2+2 seating bays, with enlarged standing areas
around the doors, with extensive use of grab-rails and perch seats.