dtokez:
I'm looking forward to trying your circuit when they do get here, hopefully I won't break the pins off! I used some kynar wire to connect to them but I tried to lift the pins in case the PCB connected them to anything else but I don't think it did
The only thing it might be connected to is a capacitor, to increase the soft-start time. You could use a multimeter to see whether the pin is connected to anything else, in particular to any capacitors.
dtokez:
I have not removed the diode bridge from them, it would be nice not to have to modify them too much. So am I right in thinking that I should connect all the emitters to the the same diode?
Yes. Make sure that each lamp you are controlling has a good connection between one of the pins and ground. To avoid damage in the event of a broken ground connection, you might want to connect a resistor of about 470 ohms or 1K between the transistor collector and the ADJ pin.