How do I get the smell of piss out of a carpet?

[LazyArsehole]

Puppy.

I've used this flash/febreeze spray with odour neutraliser but I can still smell it as I come up the stairs

You need an enzyme cleaner. You can buy them in places like pets at home

Pet shops sell a special spray which breaks down the acids that cause the smell.
It can also be used for toddler (and I guess older people's accidents) too.

Bicarb left on over night then hoover up

Simple Solution Urine Destroyer. Magic stuff.

Biological washing liquid or powder

Bicarbonate and white wine vinegar overnight.

White vinegar - the place will smell like a chippy for a while, but it fades within a day, and really works. It must be proper vinegar, though, not a non-brewed condiment.

Another vote for vinegar soak, then washing it out the next day.

What Ellapaella said. Spray with white wine vinegar. Sprinkle on bicarbonate of soda. Leave over night and vac.

Talcum powder is also great for absorbing up any nasty smells