fan is ok and i have fitted new temp sender unit still overheating, i have noticed that rad is not as hot near the senser as the top of rad think maybe rad is blocked or air locked
Remove your themostat valve and put it in a pan of boiling water. If it opens it's ok. On older engines you can run without the thermostat valve to check it. Modern engines need to warm up quicker so it is a nono. From your description you're worried that the top of the rad is hotter than where the sensor is, this is perfectly normal. Hot water rises to top of container!