2003 Ford Mondeo rear heated windscreen not working

You just got the car ? Check if any fuses for heated front screen .If not that check you are getting power and a good earth .

Just noticed it's both heated screens you are having problems with .Is the rear screen working ?

You are confusing me by saying " the rear heated winscreen does not illuiminate " and then " and the heated windscreen does not work ".Some Fords have a heated front windscreen and all have a heated rear window .If it's your rear heated window thats not working and it's not a fuse , check the wiring where it passes through into the tailgate is not broken .

I've checked behind the panelling in the boot and found a couple of the wires have been broken and reconnected with small blue plastic crimps but thses wires seem to be going to the rear light's

Sounds like no power if the switch is not illuminating or broken earth wire.check all fuses first then check with a test light wiring at rear window for power.

I am not being funny when i say this but i recommend you take the vehicle to a reputable garage and explain your problems. An hour spent by someone who knows what they are looking for could save you a very big headache. I dont know where you purchased the vehicle but it sounds like these issues where known of hence the vehicle being sold.