What MTB bike should I get?

I am keen to get a mountain bike for use in Adventure Racing weekend trail rides on sections of the Munda Biddi trail, Kalamunda, and no doubt just using as transport instead of my road bike for trips to library/shops/school etc.

I am 5foot2 so thinking a 26 not 29er, and hardtail and something light so I have half a chance of getting it over logs, so hoping to let the budget cover carbon.

Any suggestions on particular models?
Or anyone got a second hand bike they want to sell me? (in Perth).

All advice greatfully accepted.
Thanks Michelle