I figured out why they were getting kicked...
My server was seeing them as being idle and kicking them... o_O
This is because I'm still teaching them on some maps, so they just stand around doing nothing until I jump in with a mate and start to play...

So I set my mp_autokick to "0" and this disables idle kicks...
Obviously I'll change this when my bots know all the levels

Glad that one has been sorted!

Rolly