James Roffey started a thread last week that several people contributed to. I mentioned the uv hand torch I use (
http://www.gadgets.co.uk/item/X5TORCH/Inova-X5-LED-Floodlight.html).
Here are before and after photos of the same mark I identified with the torch - you will have to take my word for it that the overexposed "after" shot is the same spot.
There are several points here:
1. This small simple torch does work (I found a lot of small drips and splashes with it in the same room).
2. Use it to involve the customer - they are always impressed.
3. Show the customer the result.
4. If the customer phones back a week later to say the stain or the smell has returned, use the torch and if it is very obvious with a distinct outline it is new urine so you don't have to do a freebie job.