"There is a tangled history here, summarized in the MWDEU entry for different from, than, to. The conclusion (p. 343):
"… all three expressions have been in standard use since the 16th and 17th centuries and all three continue to be in standard use. [though different to is specifically British]"
Each of the three can be defended on semantic grounds, and on the grounds of the practice of good writers. From MWDEU, p. 342:
"From the 18th century the OED lists Addison with different from, Fielding with different to, and Goldsmith with different than."
Fowler "stoutly defends different to", but some British style guides object to it passionately, which is where Buckroyd probably got his notion that it's non-standard. In the face of the facts, I'd hope that different to is not marked as an error in exams like the GCSE — but I suspect that it is, in a sad victory for usage mythology."
