Thanks guys.
All told there will initially be 20 units of Mahdist infantry. 14 units of sword & spear and 6 units of rifles (I've had a rethink on the rifles - I'm going to do them as units 21 (not 18), each 3 bases of 3 figs and 3 bases of 4 figs. I'm going to keep the sword & spear units organised in basic units of 33 (for normal size).
So, for the Mahdists, 588 infantry figures - and they will all be a doddle to paint. Presently I've upped the batches to 50 ish.
I'll probably up the 'shock' infantry contingent to 16 units at some point - that was the intention when the lead pile was assembled but, it turned out that I needed more metal figures to 'shelter' the plastic spear armed ones and lost a unit from both the Beja and Kordofanis to do that.
Mostly, I think I need more mounted figures - presently 36 (3 units of 12) - I think that will need to be doubled. Not for historical reasons (36 is actually about the right percentage for field forces) but because it will be more fun to have more

However, apart from some of aforesaid cavalry, top of my purchase list will be enough Egyptians to do 1st El Teb. As an OOB that will probably cover most of the bases in that department - about 400 figures, if memory serves.
That will, outside boats, etc. be the collection done. Around 1500 - 1600 figures at a rough guess.