Hi there!
Essendon has a few reputable flight schools, and while each has its own strengths, you'll likely find that they offer similar quality in training. It's great that you have a convenient location! As for your question, you can definitely add an Instrument Rating (IR) to a Private Pilot License (PPL); it’s not restricted to Commercial Pilot Licenses (CPL). Good luck with your training, and enjoy the process!
Cheers!