Portable 12V power supply with UK AC output
Speakers Rating: 230V 50Hz 0.3A


Not quite right. You are describing a combined amplifier and speaker unit. The amplifier is powered by 230 V mains. The speakers are powered by the audio amplifier.

The mains power will be transformed into low voltage DC inside the speakers and this DC power will feed the amplifier circuit. (It may even be 12 V DC internally.) Your plan to use and inverter to step up from 12 V to mains and then have the amplifier step it down again is inefficient, complex and adds weight. A better option for someone with the skills would be to measure the internal DC voltage and see if the unit can be modified to run of either mains or battery.

In your case it would be better to purchase a powered speaker set with an external 12 V power supply. This could be replaced by the battery when required.


  What connector do I use for this?


1/4" spade connectors available from motor factors.