CuriousUK,
I would love to help you.. you can find me on Facebook - Andrew Shanks - Wolverhampton.
David Reed's book "How to rescue your loved one from the Watchtower" might be good: He warns, once you have got your loved one out of the Watchtower you are only half done: you still have to get the Watchtower out of your loved one.
You need to ask yourself what is the JW's motive for communicating with a non-JW? Is it to make them a JW? If that is not their motive then surely they are some of the way out of the prison already. Perhaps all you need to do is wait patiently and be a constant friend.
You could read the books of Ray Franz "Crisis of Conscience" and "In search of Christian Freedom" but be careful to keep them hidden until the right time... and who knows when that time will be??
Read the Bible.. it doesn't lead to the JW Kingdom.. read especially the first 4 books of the New Testament, the gospels: Note the way of life of the Pharisees, the religious hypocrites, and note Jesus's condemnation of them. Note how Jesus mixed with "sinners" but the Pharisees were full of self-righteous pride, and looked down on everyone except themselves (John chapter 9v34). The aim here is to hope that he will see the pettyness of the rules of the JW world, and the hardness of its leadership for himself. So yuou could somehow try to get him to look at the desription of the Pharisees in the gospels: perhaps ask him who killed Jesus and why did they kill him? I don't know how much religious talk crops up between him and you - but note he likes you just the way you are, and any big change of behaviour on your part could jeopardise the friendship(?)
It is surprising in itself that it was religious people, even very religious people who got Jesus killed. Perhaps you could be surprised at that and tell him so.. it ought toi be hard to believe that those who professed to follow Moses (you shall love your neighbour as yourself, Moses' Leviticus 19v18) could become so vicious. Perhaps ask your friend to show you everything in the Bible about the Pharisees. If you can get him showing you passages in the Bible without reference to the Watchtower then you are on the right road.
But hey, what do I know, these others have been there, and are invited to point out this may be easier saiud than done, I'm sure. comments/criticisms welcome!!