Develop a core on body/pocket carry set of items and if on occasion you carry a bag tossing a one or two more small things in there might not be the worst idea.
I would say phone, wallet, keys, pocket knife/multi tool, and possibly flashlight is a good default EDC. Of course barring specific vocational requirements.
EDC is as much an exercise in preparedness as it is one in simplicity IMO. And EDC is only important if you do it everyday.
I know your in the UK but imagine how you'd feel if you carried a knife/pepper spray/gun for selfdefense on every day but Thursday, and then someone tried to kill you on a Thursday. The E is operative in EDC and you should develop a system that you can maintain.
The items are solutions, without a problem they are meaningless.