Jane, I don't see how it's prerogative to put a view that a task that parents have been in the past been more than able to carry children and fold up a buggy to board a bus has suddenly become a civil right to carry their children and shopping in a buggy blocking up space for other passengers, particularly the disabled.
It's a privilege, not a right to use the disabled space for this purpose and parents should be practical when planning a journey by bus if a wheelchair user needs that space.
My mother over 30 years ago used to take me everywhere on buses with step entrances (Think the Routemaster on the 176 and 12 in the early 80s) and narrow passageways where she folded up the pushchair with NO problems at all, even if I was ill and needed to go to the hospital or surgery, so what has changed in a generation where taking babies and toddlers means keeping them in the buggy on the bus?
This is much a fact as much as the designs for most modern buggies and prams are not practical for use on our local buses, despite the low floor buses we now take for granted.
However if you use London Overground, there's plenty of space for buggies/disabled passengers and some stations have lift access for both which should be congratulated.