The W Adams mark for Fairy Villas features the pattern name in a fancy cartouche with a crown at the top, "Stone China" above, and "W Adams & Co Tunstall England below. The mark dates between 1891 and the early 1900s. Tunstall was an area in Staffordshire, England that included many potteries.
When you wonder about value, you have to realize that value can mean several things. You can check out a site that shows retail value like Replacements which shows how much you would have to pay retail to replace the platter. Then there is fair market value, that which a seller could expect from a sale. If you choose to sell to a dealer or through an auction, you would not get the full amount of the sale due to seller's costs including profit.
Values change quickly into today's markets as items slip in and out of demand. Search for W. Adams Fairy Villas platters on eBay and other online sales or auction sites to check asking as well as sold prices. Remember that a platter would be worth much more than,say, a dinner plate as there were fewer platters produced than dinner plates.