I found ads for several short-term apartment rentals in London, at a cost that is about half of what I paid for a hotel on my last trip there. The area (Bayswater) is one I'm familiar with, and the cost (65 GPB per night) is very attractive. But I've heard horror stories about travelers who arrive at the apartment they have supposedly rented for their vacation, only to find that they've been scammed, and the apartment is occupied by someone else who knows nothing about any short-term rental agreement.
One of the ads I saw has a "home page", with an address and phone number, but the email address in on G-Mail, and the wording of the ad leads me to believe that the person writing it is not a native Briton. (I don't mean to imply that non-natives living in the UK are somehow less trustworthy, but we all know about the Nigerian scams.)
What's the best way to go here? Is there any service in London that will check out ads like this to verify the authenticity of their claims? Also, is there any way of making advance payment to the advertiser whereby my funds will be guaranteed against fraud?