Fridge/Freezer partially stopped working after de-frost

Hi,

About 4 weeks ago I defrosted my fridge freezer and having turned it back on again the fridge no longer works. The freezer however, works fine. The model is a Creda BM21, 2 years old. I have tried and failed to get a manual from the manufacturer which might give me some clues.

I have a fuse on my wall for the fridge freezer, I assume this is not the problem as the freezer still works.

What I assume is the on/off button inside the fridge has (unsurprisingly) 2 settings. However, neither of them appears to be an ‘off’ setting. One of them makes the back heat up and the other makes the fridge a little bit colder than outside, but nothing like cold enough to store food in. The area that heats up on the back of the fridge extends only for the distance between two shelves on the inside(from the top shelf to the second shelf down). The back of the fridge at the height of the top of the fridge to the top shelf gets cold if the ‘on/off’ switch is set to ‘off’. What’s more, the fridge continues to make a noise when this setting is selected as if liquid is circulating around the fridge walls. This leads me to conclude that it might in fact not be an ‘on/off’ switch.

I can’t check the back of the fridge as its built in, in a kitchen unit/cupboard.

Could it be that the thermostat needs adjusting/replacing? If so, how could I check this?
Could it be that the element on the back of the fridge is somehow broken?
Is what I believe to be an ‘on/off switch’ really this?

I realise you can only advise me what you think MIGHT be the case and I accept that you cannot instruct me to do anything and that anything that goes wrong as a result of me fiddling about with the fridge having read your advice is entirely my own responsibility.

I would really appreciate any help or advice with regard to this,

thanks,

SwindonMan