2012 Citroen DS3 ds3 sport 2012 faults.

Last 6 months on starting engine fault light come on. A few seconds later fan comes on. turn off motor , fan still running and will only turn off by disconnecting battery or letting the motor run until warmed up . It also has a french cough on startup and will not go over about 40 kph. My european auto mechanic has changed sparkplugs, fan speed register, ignition coil, battery, fuel pump, other odds and sods and has little hair left. Has become a very expensive operation. Any brilliant ideas?