I asked the TfL customer service centre about the schedule for replacing
D78 stock. I am interested as it will cause the Tube Map to change.
Stations such as Upminster and Elm Park will be step free to train,
rather than step free to platform. I've just had a prompt email, which I
quote:
We now run about 125*new*trains on*the*District line and 10 of the old
ones. We'll probably keep the*old ones*until May 2017.

I am surprised that the schedule has gone from one train per week.

I also queried the replacement of the lift to the King's Cross sub
surface platforms. It seems they have been in service for 10 years and
10 - 15 years is usual.
--
Walter Briscoe