Is this my alternator or my battery

Some more detail, I have a UK 64 Reg VW Polo (2014) which has 90,000 miles on the clock. Whilst driving an error came up showing “12v battery not charging” this has come up before and gone away the same journey so I assumed the same, after a little while I got an error saying that the ABS has stopped working, then that the tire pressure indicator isn’t working, and more and more lights kept showing up on my dash. Eventually I had no power steering, my whole radio interface had gone off, but the engine, gears and brakes were all still fine. I was very close to home so I decided to make it back, and on the last turn my steering locked up completely, I was able to make it round one bend and into my drive extremely luckily. Is this a Battery Fault or an Alternator fault, or am I just going to have to get this checked at a garage?