Understandably, you have mentioned all the basic elements taught during the PPL.
You seem comfortable following a preordained plan. Perhaps you wouldn’t be as comfortable were the plan to change. In fact your friend unwittingly may have given you some good advice.
You will find one of the best ways of improving your SA is to place yourself outside of your comfort zone. I have flown with pilots that have planned to the Nth degree – they think they have everything covered and then the runway changes, they find themselves flying the missed and it all falls apart.
So choose three airports – have a look at the met and the wide area NOTAMs but don’t think too much about which runway you will be using just ensure crosswinds limits will not be an issue on the day and set off. Work it out on the hoof so to speak and see how it goes. You may find you learn a great deal and your SA improves significantly as a consequence – not on that flight, but on subsequent flights.
Next time you fly think of a time mid flight – it could be 11.10 for example. When 11.10 comes you have had an engine failure or a temp warning as you prefer. I bet you miss the time and I bet you find the experience interesting.
Next time you pass over an airfield on route somewhere give them a call on the spur and ask if they will accept you for a coffee. It will improve your SA.
In each of these scenarios think about the process you will go through when the “event” occurs. Just by planning for these events you will find your ability to cope with genuine diversions and even pre-planned routes improves immeasurably and with it you’re general SAs.
If you are serious about your flying any pilot should get to the stage where he can sit in the cockpit, decide on a destination a few hundred miles away in the UK, and assuming VMC, he can plan the route and be airbourne in less than 15 minutes. It may be hard work but next time your SA is challenge in earnest youw ill be amazed how much more spare brain capacity you have because you have been there and done it before.
In short these are all techniques that help you to get use to planning on the hoof - it is when the plans go out the window that you will find so does your SA unless you know how to go about it - another subject in itself!