If you have replaced the heater and its still not heating and you dont get 240v to the heater unit then its going to be the main control board.
As for a no heat fault its only ever a fault heater or control board. As on the heater as you will have seen it comes complete with the thermostats and sensors on it. So if after replacing the heater its still not heating then it will be the main control board itself at fault here causing this.
If you access the control board and just inspect it for burning. But from the fault you describe this is going to be a faulty control board.
Now this is a very expensive part. As the board itself is £90 from Hoover direct so not a cheap part im afraid.
Sorry its not good news but if you need anymore info just get back to me.
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