[ophic]

Wear and tear for a carpet is usually calculated on expected lifetime. This is normally around 10 years iirc. So you wouldn't expect 2/10ths of the value back, leaving the tenant liable for the other 8/10ths. Yes they are liable for the whole carpet, not just the stained bit.

So 8/10ths of £150 is £120. It's up to you whether that £70 difference is worth arguing over.