I can't recall the name of the hotel I stayed in but you can get a bus from the Barbican (a few minutes from the main square)to Aushwitcz . It's about an hour away and they show you a video about it on the bus as well. There is a guide when you get there and you only pay for the bus(about £12) as it doesn't cost anything. You also get a guide.

Pretty harrowing experience but I'm glad I went