Taking payment after the booking is normal practice for agencies. They work on the assumption that you'd rather get more bookings than run off with an extra few quid.

At ?20 you're better with them than most of the other sites, and it's possible that they're not specifically trying to scam you. I wouldn't go for it, though.

Do a search for the site, you can see that the results are mostly recruitment ads. There's one ad aimed at clients on a free classifieds site, and two websites which they've created for individual escorts (neither of which appear on the agency page). Search for the addresses of those two sites and you'll see that they're not widely publicised: they just have profiles on a couple of free listing sites.

So as far as the web presence goes, you could do better yourself for free. Now, they might be putting their effort into offline advertising. If you can see for yourself that they're putting time and more importantly money into finding clients, then you can at least feel confident that they're using that fee to help you and not just pay for their holidays. A good example would be if they tell you that they have an ad running in a magazine which you can pick up and check out yourself. If they tell you that they get all their clients through word of mouth or are otherwise unable to prove that they do anything but bullshit, I'd leave them alone.

We just had a good thread on the subject of non-sexual escorting, so have a read while you're here. http://www.saafe.info/main/index.php?topic=981.0