Martyn … thanks for the clarification. I am far from an expert on this stuff. The V3 Beta sketch seems to set the BT serial to pins 17 and 16:
SoftwareSerial BTserial(17, 16); // RX, TX
The schematic on the post indicates RX and TX on D18 and D19.
I just changed the sketch to match my wiring and that sorted things out for me.