Check your fuses first, look fo the Electric connection for the rear screen & check if there is feed to it. Look in your hand book, Its not so often the rear screen goes carput.
Hi, check that there is no break in the elements across the screen, if that;s ok give the screen a good clean & try. other than that take the car back to where you have bought it ask them to fix it, do not back down. ( Has the car got a warrantee)
Check the manual for the relay location .. it's more likely to be that.
If the indicator light works, but the heater doesn't, then also ckeck the connections and the cables at the rear. If a hatch, cables can get damaged between body and rear tailgate frame.
Sorry for late reply .. the Dealer who sold it to us said it was covered by Network Q warranty but when we said we had problem they said it was checked prior to sale so we must have damaged it!!!It was previously a hire car but was only 9k on the clock I will never trust Network Q again xx