[Margaret Pilkington]

You need to find the place where the wee is......bare feet works well......unless it is a male cat and it is just spraying, in which case you have to trust your nose and treat the place where the smell is strongest.
A solution of bicarbonate of soda in water works well......sponge the area with the solution and sop up any moisture left behind with old towels.
You can sprinkle dry bicarb onto a place where the cat has wee'd...leave it overnight and then vac off. You may need to repeat this more than once to get rid of the pong.
Thankfully bicarb is cheap.
There are other commercial products on the market, but they aren't as cheap as bicarb.
Hope this helps Shaz.