Hotpoint Fridge Freezer FFa90

I have a problem with my Hotpoint FFA90 Fridge Freezer that has been bugging me for a long time. There is a large “crashing” noise from the back of the unit – this I understand is normal defrost. However, a few minutes later there is a puddle of water appears in front of the unit. This happens very frequently. The bottom drawer is also slowly getting blocked with ice, unusual for a frost free freezer. I have removed this once but it has since appeared and is steadily growing. Please can someone give some advise to what may be causing these minor problems.