Deposits - Eaten Carpets

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QUESTION:
I had a lodger in my house, where I also live. When the lodger moved out all the rent was paid up and the keys handed back. Unfortunately, she liked to oil paint in the room and managed to get oil on the walls and cabinets. Worse, the lodger had a hamster which has eaten away at the carpet in two corners of the room - the damage is around the size of a large mobile phone and is down to the underlay. Would it be un-reasonable for me to withhold all the deposit and charge for a new carpet?