Steve150
I can fully understand your questions, I recall it didnt make sense to me.
Let me explain.
ATC if you are not on an IFR flight plan (which you will not be) actually have no interest in where you are going or what you are doing. That is your starting point. To the extent they are interested, their interest goes as far as the area of airspace they control.
So lets assume you depart Southampton (for no other reason than it is as good as anywhere). Now Southampton is within class D airspace. Class D is controlled airspace so Southampton will want to know what your intentions are within their airspace and are entitled to either accept or deny your intentions. You could for example tell them you wish to track to Goodwood and then return to Southampton. If they have no conflicting traffic they will be happy to agree for you to route direct to Goodwood. As soon as you leave their class D airspace they have no interest in what you are doing. To the East of their airspace you are in uncontrolled airspace or OCAS - you can do as you like. For example having got to Goodwood you might decide you will pay Lyd a visit. No one cares and you don't have to talk to anyone . The only possible airspace that isn't OCAS en route is Shoreham and you only need to talk to Shoreham if you wish to transit their ATZ. Having got to Lyd perhaps you might decide to route back to Southampton. Once again no one is interested in your change of plan. Eventually you will close on Southampton's class D and once again they require to know your intentions and agree with you a clearance through their airspace back to the airport. So hopefully as you can see once you have departed an airport and left either their ATZ or class D veil into OCAS no one cares what you do or where you go all the time you are outside controlled airspace or outside an ATZ. Now many PPLs take comfort in talking to someone on the radio or feeling there is someone to talk to. That's fine. You will find in time it probably doesn't give you the comfort you are looking for, but that takes time. So in my example you might wish to talk to Farnborough who will provide you with a basic or traffic service between Southampton and Lyd. Again it is important to understand what they can do for you. Under a basic service very little. Once again they couldn't careless where you are going and how you get there. If you decide to do ten circuits of Brighton its of no interest to them? Under a traffic service its helpful for them to know your route because their job is to warn you of conflicting traffic. However once again if you wish to orbit Brighton for half an hour its no concern of theirs.
I hope you are getting the picture. New PPLs think in terms of flights being from A to B along a predefined route. That is how we all start. In reality you could depart Southampton clear their CAS and fly to Scotland without talking to anyone or telling anyone of your intentions. No one cares as long as you don't want to transit their bit of controlled airspace.
With more experience you may find that is exactly what you end up doing. You might depart Southampton and think its a nice day I will have a potter along the coast to Brighton, and then having got to Brighton and finding you are enjoying yourself, think I will take a trip to Manston. Perhaps at Canterbury you decide you would like to overfly Manston so you give them a call and request permission to transit their ATZ - permission is given and off you go.
Now some places like to know if you are landing away, because if you don't say you are they might send out the troops when you dont arrive back a few hours later. A few are keen to know where you are going but in reality they have no good reason to know or ask. In my experience you can usually say "G-XXXX is departing to the East with the intention of landing away".
We hear so often over the radio G-XXXX is on a navex, or sightseeing or routing to Lydd via this and that, in reality outside controlled airspace no one cares and you can make it up as you go along.
So to your first question similarly no one cares about your unplanned diversion. If you think I might like to call into Lydd for a coffee - go do it, the only person you need to speak to is Lydd to ask them if you may - its their ATZ and within their gift.
Now as I indicated earlier some places will get concerned if you have said you intend to land away and don't return when expected. If that is the case and if you change your plans and land away give them a call on the land line.
Does that make sense?
Inevitably you have tricks and tips to learn to make this all work in practice, but so many new PPLs have very little concept of what service they are really getting from ATC and the extent to which we are free to go where and as we please. It is a wonderful privilege I guess.
Today I went to Bembridge. Bembridge doesnt have any "air traffic" most of the time. When you depart their is no one to tell where you are going even if you wanted to. After leaving because it was such a glorious day I decided I would take in an orbit of the Isle of Weight - so I did. There is a bit of Southampton class D to negotiate so I asked for a transit which was given. Happy days.