Oils and fluids?

I need some advise on what to use in my R   

I'm going to change the coolant because I have no idea whats in it and I've topped it up with some stuff from halfords but since then I have read you shouldn't mix different coolants.
What coolant should I use?
Does it even matter along as I don't mix different ones together?
And how much will u need to fill the R?

I'm also going to change the gearbox, transfer box and diff oils for peace of mind.
What oils should I use for these?
how much will I need to fill each one?

Also I need some power steering fluid, what should I top that up with?

antifreeze was the blue one bill cant remember what its called lol

gearbox oil holds around 4.5ltr
transfer about 1.5ltr
rear diff around 1.5ltr
all from empty
use 75w/90 semi synthetic in all the above

power steering fluid is same as universal auto gearbox oil, the red stuff

Cheers bob, any reason you say semi-synthetic for the gear oils? Would fully synthetic be a more expensive but better option or should I just stick with semi?

I'm sure I've got some of that red auto box oil in the garrage somewhere so that saves a few quid lol

we always have used semi synthetic never really had a problem with it and cant see the point in running expensive oil in an old worn box as it wont make a scrap of difference or make it last any longer
bit like all the additives you see everywhere, none of them really do anything other than make a bigger hole in your pockets lol