MadEngineer:
What kind of plug? One of these?
You may require one of these tools that you clip on between the plastic and your work area. The tool then takes the heat instead of the plastic
Edit: 6 Piece Soldering Tool Kit | Jaycar Electronics New Zealand
Yep, that the plug.
Just plug it into a well made socket and it holds the pins in the exact right place while you solder it