Im an ED nurse.
If you are just talking about walk in patients, we have GP attached to our ED. Of our ambulatory aptients, at triage we send over on average 30% of patients to the GP. Much higher if you include childrens ED, it is closer to 70% in childrens. But adults only its 30%. However some could see a GP but by our triage its not appropriate, id guess another 20% are in ED when there would be better alternatives. Minor injuries we redirect before they book in to the walk in centre, unless there is a legitimate reason why they cant attend, so i dont have even estimated stats there. Then theres patients who come in because they literally have no place else to go, regular attenders who are in because they want and sandwich a hot drink and few hours out of the rain. Do they need to be there, no, but whats the alternative for them? Im more than happy to give them a sandwich and a cup of tea, try to move them on when the department is full and we are running out of seats, but if we have plenty of spaces, they can sit for a couple of hours.
However, most patients in the dept are brought in by ambulance, and waiting for ward beds. So looking at the whole department, id estmate its along the lines 30% total could utilise other services.
However! Some brought in by ambulance probably could have avoided admission if they had access to primary care when needed, if an infection had been seen to quicker, it wouldnt have escalated till they needed IV antibiotics. If waiting lists for surgerys werent so long, etc etc.
Its a complex situation. A&E isnt viewed how it once was, its now viewed as an alternative to GP's, because people cant see GP's. But people attend with a "GP" problem, knowing the pressure on departments, and still get angry at the 8, 9, 10 hour wait to be seen. Its frustrating as staff, but i get it, i understand theres no alternatives.