It can be a bit of hassle. In looking at your pics I noticed that the bottom rim appears to be ground. Now here in the states that is one way we determine Fostoria America from the others. Fostoria issued a better quality of glassware with more attention to detail. In looking closely at your pics, I would say yes its Fostoria America.
I only learned last night from a friend of mine that a lot of Fostoria was shipped to England. Certain peices were made for the English market and command high prices here from the collectors. This might be an interesting area for someone to explore. Terry