hello, i could do with some technical help if anyone can offer some?

I have a Hotpoint Mistral Plus - Fridge Freezer with the same temperature problems, fridge doesn't cool, sits around +20c but the freezer works just fine.

I ordered a thermistor for the fridge and took off the back section inside the freezer which according to the numerous posts, is where the wire needs replaced. There was 2 thermistors in this section, 1 for the freezer temp and 1 attached to the metal grill thing (forgive the technical terms!).

The thermistor i received from whitegoods.co.uk was too short or too long to replace either of these ones in the freezer, so i began to think, how would these thermistors control the temperature of the fridge if they are both in the freezer, so..........

Into the fridge, took of the light unit housing and voila, another thermistor, this one was connected to a board sitting at the back of the front display panel, which i had to lift off the top of the fridge! However the thermistor I recieved did not have the same plug attachment size, it was yellow though.

The fridge has been turned off 36 hours, when i took of the panels and light unit, there was no visible build up of ice and the fan spins freely, the fridge buzzes and burbles a bit when it is cooling but nothing that sounds serious.

Does anyone know which thermistors i should replace in the off-chance i can get this working again. Not having a fridge is a real pain in the a*se