Possibly looking to switch from Nikon to Canon ....just for a change (Note I had Canon before Nikon & will not get drawn in to one is better than other debates

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Outfit must cover following :-
- Image quality / sizes good enough for Alamy
- Will shoot Landscape (50%), Portrait / Candid (20%), Wildlife (20%), Sport/Action (10%)
- Not interested in Macro, or flashes.
- Want circa 10mm at wide end & 400mm at long end (ideally IS)
- Maximum 4 lenses
- Not adverse to 3rd party lenses
- Would prefer s/h to new
So budget is £2,500 ....what would you advise ??