Thanks for that.
I know there is a design issue with the placement of the thermostat on the early models of this fridge. I have had issues in the past where the fan has started ticking. I had a look online and found some instructions on how to remove the ice that builds up around the fan, causing the ticking. This time, the fact that the water dispenser had stopped AND the fridge wasn't ticking - it just wasn't working - was a bit concerning. Anyway. I think the water reservoir must've frozen up (a first) and something about the ice around the thermostat on the fridge side had just made the cooling stop working altogether. Odd. Anyway, it's all been de-iced and put back together and it seems to be working fine now.