Beko CDA647 FW

Hello,i need a bit of help please.My fridge/freezer has thawed out and is making a gurgling/sloshing of water sound.I pulled the thermostat, it looks ok,and turns the fridge on and off manually,it is also switching itself on and off via the thermostat,but not getting any colder.I did some research,and this model had recall because of a fault with the defrost timer.Maybe this one never got fixed ? Can anyone tell me where abouts on the thing i will find the defrost timer,and where i can buy one.Should i buy a new thermostat first ? Thanks very much for any,and all suggestions. Mick.