Firstly for an unplanned diversion during a leg of the route whats the procedure for talking to the ATC
My last unplanned diversion, I called up Norwich and told them that I was being pushed north by a thunderstorm and might end up inside their airspace. "Fine," they said. Then I told them I wasn't going to outrun this line of storms and was going to land at Norwich. "Fine," they said.
If you don't want anything you don't need to talk to anyone. Before I called Norwich I hadn't been talking to anyone (I think I might have had London Information tuned in with the volume turned down, don't remember). If I
had been talking to someone I'd have told them I was changing frequency.
And secondly if when I have my license and want to take passengers up sightseeing around the local do i just say that or will they need to know my route/turning points?
You don't need to say anything to anyone ...
unless you'll be doing something that they will be interested in.
So in one case my passengers wanted to overfly a village and identify a house underneath someone's instrument approach path, so I called them up and said "do you mind if I spend a few minutes sightseeing in your instrument approach at such-and-such a height".
Or you might get asked "what's your operating area and level" or somesuch, in which case you might say you'll be to the north-west of the field at around 2,000' or whatever.