Still a little lost on what oil I should be using in my car. And after receiving various different answers from different sources I am now even more confused!

My cars on the annual service regime and my manual says I should use the 502.00 spec oils. Now this spec in itself is not very clear because it lists out several different oil grades: 0w-30, 5w-40, 10w-40, 5w-50, 0w-40 & 5w-30. Now which of these oils should I be using, and is any particular one better than another?
The Stealer I bought my car from says I should be using 10w-40.
Most websites/forums tend to suggest 5w-30 is the way to go.
Halfords says I should be using 5w-30.
Can anyone what oil I should be using and out of the various options which is the best oil to use? Many thanks