Need Rail and public transport help for UK

Hey guys and gals
now im doing two contiki tours an egypt one and european vista. now in between the two I have a week and a half in london. i am staying with family out in Reading and am enquiring about transport. Theres a few things that I wanted to do in London on a few days so I think i will be spending most of my time in the city.

I have looked at so many different rail and train and bus web sites ive gone and gotten myself all confused. lol.
so i was hoping that someone might be able to help me out.

I would just like to know how much (cheapest possible!!) a train fare would be from Reading to London Paddington station is? And rather than just getting a one way or return ticket is there any way of saving if I buy like a week pass or something?

And also along with this I would love to know more about the Tube. everyone goes on about it, and using it as the main form of transport but Im just thinking of the money now, how much am i going to be looking at?

Also after my Contiki Vista tour im heading up to Manchester or close near there. I am catching the train from London up there. and I have no idea about public transport within that area. I am hoping to visit a friend in Chorley which is approximately 45 minutes from Manchester and im like yeah ummm how do i get there lol.

So please IF anyone can help me out with this or direct me somewhere where i wont get confused with fare prices etc or if you live in London and you might know could you please get in touch with me.

Thanks a HUGE bunch!

Celeste