Can anyone confirm the interchange arrangements between the Tube and
DLR (and indeed other railways) and what the charges are. It's not too
clear.

An example journey.

Blackfriars to Blackwall.
I take the the District line from Blackfriars to Tower Hill.
Swiping in and out at both stations. Oyster deducts a zone 1 single
fare.
I then join the DLR at Tower Gateway to Blackwall. Swiping in and out
at both again. This time what is deducted?

The total fare for the entire journey should be £2.00 ie
the zone 1-2 fare. However I don't think it is.

This is unfair as if I bought a printed ticket. I could do this
journey for £2.20 With Oyster I pay more.

This also applies to similar journeys where there are seperate
stations.
Such as at Shadwell with the connection to the East London line.

So how does it work and how much do I pay?

ANDY