R has a funny habit in standard UK/Australian English. At the end of a syllable, it seems to disappear (in UK English it actually goes to the back of the throat, a bit like a yawn; in Australia, the R disappears entirely and the vowel is usually long). US speakers often use a different pronunciation of R, so they can afford to pronounce it every time.
The pronunciation of /stir/ sounds like a clipped version of "steer".