Thanks, it is much more clear now.

Last question; in order to calculate the total power supplied am I right in thinking it is the total voltage supplied (so in this case 30V) multiplied by the current which was calculated through the resistor of 54mA (taking into consideration the voltage drops through the LED and diodes), which is equal to 1.62W total power.

This is dissipated between the resistor (Voltage drop across resistor x current flowing through circuit) and LED (voltage drop across LED x current flowing through circuit).

I believe the original calculations also included the voltage drop across a bridge rectifier, which also has a power dissipation component. So, you've got the right idea, just missing a few diodes.

Why do you want to know total power?

 

The resistor sets the total current through the system. So if you know you're drawing 54mA then everywhere in the circuit you're drawing 54mA. So 54mA times the supplied voltage (don't subtract anything from it) is
30 x 0.054 = 1.62 watts. So, yes, you've figured it out correctly.

Remember, changing the resistor changes the amount of current through the system. If you drop the resistance you increase the current. Thereby you increase the wattage.