We love Disney Fairies at our house, but merchandise is hard to find... and I know that there is stuff available in the UK that's not made for the US.
I have no help for you, just a story.
We were at WDW in April with DD5, who reads Disney Fairy books and is somewhat of an expert (on the book-fairies in particular). Sitting on a bench, waiting for Peter Pan to come back for autographs, she's looking around and spots a girl in a store-bought fairy costume. She recognized the costume right away and was able to correctly identify the fairy. The girl's mom said that her DD hadn't had anyone all day (and it was 2 now) recognize who she was!
Not to dissuade you - I made DD a Rani costume for Halloween and she has absolutely no problems telling anyone who will listen who she is, what Rani's talent is, and all about her adventures in Mermaid Lagoon!
Good luck!