6 volt LT at 2 amps

[pwdrive]

Maybe post the voltages with the 5 ohm load connected.....The regulator output voltage, the regulator input voltage and the AC voltage input to the bridge rectifier.
Lawrence.

but if I had of guessed wrong would it have been REALLY bad or just heated up and a bit of smoke before cutting out the RCD?
 

It depends how much it's heated up, that would depend on any fuse rating or if no fuse how quick you are with the power on/off switch.

For an RCD to trip there needs to be a current flow between live and earth or neutral and earth.

Lawrence.