Urine Off and Yard Cleaner are two different products, if its the company I think (R&L Products)...
I use Yard Cleaner from them and I dilute it more than they suggest. It still does the job as well but I use much less product. I would imagine you could do this with their Urine Off as well.
If you Google them they do attend a few show each month, mostly cat shows, so you might be able to pick some up locally and save yourself postage costs. Mind you the delivery cost of £3.78 isn't too bad on the large size (3.75 litres) you can spend that much on parking!
Good luck - great stuff isn't it :)