Hello Adrian954,
The .30-06 is a good choice.
I went to Limpopo area in South Africa, for a month not many years ago and did some work for a Safari Company.
They issued to me a .30-06 and 220 grain round nosed jacketed softs (Hornady RNSP).
With it I culled many female wildebeest, impala and others plus, I did a bit of hunting for myself, in the company of a PH and tracker, like any client would do.
Likewise, I have used this load in Alaska where I live and it was effective.
The .30-06 with that load worked like magic for me.
So, I recommend it.
But, as Phoenix Phil said, it seems a bit light for eland.
However, many eland have no doubt been taken with it, just the same as here in N. America: The .30-30 is a bit light for elk, moose and bear, nonetheless many have been taken with it.
All that being said, I prefer larger calibers for larger animals and would prefer something like a 9.3x62 Mauser or even the slightly over-powered for most antelopes and deer - the incredible .375 H&H.
Neither of those are necessary and I only mention them because they are my preference for antelopes, mostly because I am a dreaded "gun nut" and I find the "African calibers" quite interesting / historically significant.
However, I repeat myself in that the .30-06 is a very good African "Plains Game" caliber for many reasons, not the least of which is that not only does it penetrate well when firing heavy bullets (180 - 200 - 220 grains) but it doesn't kick too hard and best of all, ammunition is usually always available wherever in the world that hunting is part of the culture/economy.
I believe it was the old time American writer Townsend Whelen (the .35 Whelen cartridge is named after him) who said: "You can't go wrong with a .30-06" and I find comfort in that.
Cheers,
Velo Dog.