Vauxhall Zafira engine cuttung out

hi, i have a zafira 1.6 club with 103000 on the clock, it has been cutting out from time to time as i drive about 10 miles later the car kangrooz so i slow down and as soon as i put the clucth down to go into a lower gear the revs die and the engine cuts out and then won't restart, i will wait about 10 min and then try to start the car and it will start like thers nothing wrong?????
i have cleaned the throttel body and all the cornecting pipes changed the battery because i need a new one changed the flue fillter, air fillter, sparkplugs, checked the cat converter, flue pump, flue pump rely, all fuses, vac sensor.

and still the same i dont know what els i should do because my wife wont go anywere in that car i was thinking of saleing it but i do like the car and dont want to sale somthing to some one that may be unsafe.

what to do???????????????????????????????????????????