For another perspective from the United States: The American Heritage Dictionary lists "bit" as a possible past participle, in addition to bitten, with no usage note that such use is non-standard.
A "bit" about The American Heritage Dictionary: Its stance on a number of grammatical issues can be, admittedly, liberal sometimes. But, its usage panel is a list of who's who of Americans working in the fields of linguistics, literature, criticism, etc. Generally, it will include a "usage note" if a word is considered non-standard or if there is a debate about a usage. These notes are wonderful, as well as are the pictures in the hardcover version (the online version still has the usage notes). The dictionary is actually great reading. Highly recommended!