Not a lot of autographs there that I would be willing to give an opinion on but the pricing seems sensible. They also point out that the certificates of authenticity that accompany some items are incidental - i.e. have little or no bearing on their assessment of the item's authenticity. You might ask - well why even mention them, then? But that's a minor quibble and obviously a Zarelli or similar is a selling point.
I would probably be willing to purchase something there and would expect to be able to obtain a refund if dissatisfied from some reason.
I've come across the site before but never really looked through it in detail. I believe Robert Sauders actually lives in Australia but I guess the site was set up when he lived in the UK. Everything I have looked just now at looks legit. He is obviously not giving the stuff away but why should he? Anyone who can get John Constable and Linda Lovelace on the same page (Miscellaneous) has to be applauded.