Have recently had turbo replaced on my 2009 Titanium. TDCI. Have noticed that if I switch air con on when at a standstill I get immediate smell like exhaust fumes. It works ok...still chills air. Don't notice it if I switch on whilst on the move. Any tie in with turbo replacement?

It is quite plausible that if you have fumes under the bonnet they only get into the cab when stationary. I had something similar when my injectors were leaking.
 

Have you had your pollen filter changed  recently with the air con mine smells like a damp warm dog(needs changing badly have a butchers at that first as that is supposed to get rid of fumes/smells in the cab. If old it can smell bad when air con switched on

I'd be checking the exhaust side connections on the new turbo first, if they're accessible?  Might be as simple as a loose clamp...

Also check oil breather pipe hasn't been damaged as burnt oil fumes smell similar to exhaust fumes when entering the cabin.  Common issue on the Focus' as the plastic clips break easily, not sure if you'll have the same style clips.