hotpoint fridgefreezer ff63?

Hi
I'm after just a little bit of advice if possible as trying not to buy the wrong part as I've already done this once.
I have an hotpoint fridge/freezer ff63 and its fault was that over a month or two the freezer froze into a lump of ice. After defosting it the last time, when turning it back on it didn't freeze down cold enough. After having a look and getting some advice I replaced the auto defrost believing that is why it kept over freezing.
But didn't really make much differance and still not cold enough. So has left me believing it's now the thermostat?
But there is just one or two things that isn't right with it that I'm trying to check out before I buy.
The internal light in the fridge is now only half as bright as it once was, also does not come on at all when the compressor is runing!
The fridge thermostat seems fine, can adjust the temp ok and works well. The problem is just with the freezer

Many thanks.
Paul Stone