Problems with my 306!

i recently brought a V reg 1.4 306 and i am loving every bit of it apart from a several problems.

It has ac BUT its not working so my mechanic says i need to take it to a car AC specialist. when i press the ac button the light for it turns on but there is no noise or anything and as far as i can tell the air does not come out colder.

the engine heats up to the halfway mark (Although i have been told this is not a problem) anyway yesterday i was in a very congested multi storey car park and had my fan on the lowest temperture but it was still giving out hot air as though the temperture for the fan was on max. furthermore, there was a slight engine sort of smell coming thru the fan, at first i thought it may have been from the fumes in the car park but then wen i got the car out of the car park i noticed the smell was still there.

is this anything to worry about? got any ideas what the problems might be? this is my first car and i would like to keep it untill i finish my degree (3 years hopefully!)

thanks

Doesn't sound too good i'd go and get it checked out by the garage. better safe than sorry.