Updated
Tried the app earlier.
1)With phone on USB connection to USB port on PC screen, shows 100mA
2)With phone on USB lead connected to 1.5A rated charger that came with phone, shows 310mA
3)With phone on USB lead connected to a mains surge protector block with USB charger built in, shows 870mA
4)With phone in Brodit USB holder, shows 430mA
5)With phone on USB lead connected to top USB socket, shows 310mA (this socket is the one the Brodit normally connects to)
6)With phone on USB lead connected to lower USB socket, shows 480mA
7)With phone on USB lead connected to 12v cig plug, shows 860mA
As it stands, 1) doesn't charge the phone (it used to on my previous HTC One M7), 2) and 3) do. Can't confirm the others as I just plugged in long enough to test current rate. Best guess is that the app reads low, possibly dependant on what the phone is doing at the time? Am also beginning to suspect that different leads have different abilities.
Alan