Is it more or less than 2 years since you bought the Macbook?
Under Australian/EEC consumer law Apple (or anyone) must provide a reasonable warranty commensurate with the reasonable expected life an electrical product, which the ACCC/EEC has declared as 2 years.
If it is under 2 years take it up with Apple who is obligated to repair it at their expense.
Either way I would search for any known issues with your model. If there is you have further rights to have that rectified.
One thing you did not make clear was is the issue with the battery or mains power?
Within the EU it's not so simple. For us the Mac must have been bought from a supplier within one of the EU's 28 countries. When I enter a repair job in Apple's GSX, I am prompted to select wether a European Consumer Law Claim is applicable. For it to be applicable there has to be a hardware fault and no sign of damage. Most importantly, this does not cover business users, only consumers. If the Mac was bought under a business name it will not be covered. Also, another must is the the owner must have his original bona fide receipt or invoice, and it has to show the suppliers details. If no receipt then there's no claim. A claim form is completed and signed and the fault diagnosed. If the Mac is under 2 years old the repair will go through automatically if the submitted paperwork pdf's are in order, if over 2 years old it's marked for review by Apple and there is a small delay before approval. I've never seen any justified claims refused. I've no idea if similar schemes are available elsewhere.
As already mentioned, take the MBP to an Apple Store Genius Bar for a free diagnosis. If you attempt the diagnosis yourself be careful not to damage any of the connectors, some are fragile if you are not used to releasing them. If you buy a used logic board it will contain the serial # of the MBP it was stripped from and can cause software issues. Additionally, you don't know what care was taken in removing the board. Some people have never heard of ESD precautions.
MacBook Pro Retina logic boards do fail, as do the retina displays, as any electronic part can. Even electronics built to military spec costing multiple times more than a MBP fail, I know as I used to repair them, so a high cost doesn't indicate a product will never fail.