I've just got myself an Oyster. I live in zone 5 and work in zone 1.
However, I'm extremely confused, despite reading lots on the topic! I hope
someone can clarify the situation for me.

I ordered myself 3 months of Travelcard for zones 1-5, thinking that this
was the best deal for me. However, many people have told me that pay as you
go would work out cheaper for me. Fine, but I can't find anywhere that I can
work out what it would cost me!

I live in zone 5 on the Piccadilly line, and have to travel into zone 1,
change to the Northern line, and travel a few stops to my destination also
in zone 1. I then do the same in reverse to get home.

This will make up the majority of my daily journies. Occasionally it may
differ, but it will still be zone 5 to zone 1 and back, perhaps with a
change. I will rarely use any other form of transport, and will largely only
use it Monday to Friday.

So will pay as you go really be cheaper, or should I stick with what I've
got? And if I do need to, is it possible to change now that I've bought
these 3 months of Travelcard?

Many thanks in advance.