Well, a hunt for any kind of manual was almost fruitless but I did find this, which MAY explain the controls.
http://preview.u-manual.com/preview-manual-for-free-118927/freezer-refrigerator-newpol-xv120el/page-8.html
Be warned; the website is awful. This alternative may be better:
http://ns323666.ip-37-187-156.eu/manuals/New%20Pol%20Freezer/New%20Pol%20XV120EL%20Freezer.pdf
The manual is pants as well.
It COULD just be it needs a good defrost and any drainage pipes clearing out. (Plastic covered net curtain wire is good for that)
xxx, April 2016