Thanks to all who participated in the survey on pronunciation of the “-man” suffix in such words as “policeman” and “gunman.” I reported on the results yesterday on the Lingua Franca blog.
One finding I didn’t report was the difference between U.K. and U.S. respondents. For certain words it was rather dramatic.
Here is a graph showing respondents from the U.S.:
And this one shows U.K. respondents:
Generally speaking, U.K. respondents use the schwa more often than do American ones. Here are the three words with the biggest difference:
My hypotheses for this relates to the general idea expressed in The Longman Pronunciation Dictionary, that reduced-stress schwa-vowel “-man” tends to occur in “well-established formations.” The three words in the chart above are nothing if not well-established–and were established in the British Isles long before there even was a United States.
Also supporting the hypothesis is results on “lineman,” which I threw into the survey without thinking about the fact that it’s a mainly American term, either as a football position or the job memorialized in Glen Campbell’s song “Wichita Lineman.” (Google Ngram Viewer shows much greater use in the U.S.) Sure enough, U.K. respondents–to whom it’s unfamiliar–significantly outnumber Americans in reporting an equal-stress /æ/ vowel in “lineman.”
notoneoffbritishisms.com 
weatherman/weather man. As one word it refers to that radical group in the 60’s. From my UK heritage I think of the man who does the weather as two words, not one. But them my age might influence that! Better start taking that into account – it impacts pronunciation/emphasis
I think the mailman is largely found in the Americas too, so I’m not sure how that affects the theory. 15 years in Canada, and I still eagerly await the schwa’d postman.
In Britain only linesman is in use nor is garbageman used at all (dustman) except in the Chico/ Groucho Marx quote “Emperor the garbageman is here”
“Tell him we don’t want any.”
Further, I think the reason that ‘Garbageman’ and ‘Mailman’ come out in the UK as a non-schwa is because we think of them as American words and therefore pronounce them as we have heard them pronounced by Americans.
I mainly know “postman” from the song “Please Mr. Postman” which definitely uses the “can” pronunciation (US, MidAtlantic).
Following on from Sam C, from the UK point of view “mailman” is an Americanism we would never use, and “postman” (sans schwa) is the regular term – hence the Marvelettes’ song resonating with the Beatles. So – putting aside the alliterative attraction of the song title – was “postman” more common in the US in 1961 than it is now ?
I agree with Michawl that we don’t have a garbageman. We have instead a binman, which in my case at least, is pronounced as in woman and postman etc.
Mr Sandman, send me a dream.
The schwa version of postman is in common use here in the UK – it’s used for our most famous postman of all.
Plenty of comparison in this video since most of the rhyming lyrics end with “-an” words.