In the previous post, I discussed Britishisms in the American novel The Plot, and several British commentators zoomed in on the line “she straightaway found a job.” It was contended out that the actual British term is “straight away” (two words).
Backing up a bit, I see that in the early days of the blog, I did a post on “straightaway” and a separate one on “straight away” — things were a little bit chaotic back then. But I didn’t sort out the one word/two words issue, and I will try to do so now.
But first I’ll point out that the American equivalent is “right away” (always two words) or “immediately.” Here’s an Ngram Viewer chart showing frequency in American books:
Muddying the waters a little bit is the fact that one-word “straightaway” has another meaning, labeled “chiefly U.S.” by the OED: “A straight course in rowing or sailing. Also, a straight section of a road or racecourse, etc.” With that in mind, we can say that the two-word version for “immediately” is more common even in the U.S.
So now let’s compare the two-word version in Britain and the U.S.:
That is to say, it’s definitely a NOOB.
Finally, were my commentators correct in saying the two-word version prevails in Britain? The OED would indicate not. Here’s its entry:
The citations show a classic progression from two words, to hyphenated, to one word.
However, Ngram Viewer supports the commenters. Here’s the chart for the two versions’ frequency in British English. It shows that in 2019, the “straight away” was used about four times more frequently than “straightaway.”
Not to state the obvious, but the one word/two word distinction applies to written language, rather than spoken, where the question is moot. I imagine that to some extent the commenters were expressing their sense that there is a pause between “straight” and “away” when they say or hear the term.
Finally, one commenter, Tony C, said: “The word order is wrong in British English as well: ‘… she found a job straight away …'”
I have a hunch that he’s wrong, that both sentence structures are found in British English (see the Daily Mail quote from the OED), and in fact that this can elucidate the one word/two word issue. That is, before the verb, “straightaway” is one word, and after (as in Tony C’s rendition), it’s two.
But full investigation of this point will have to wait for another day.
notoneoffbritishisms.com 
Interesting. As an American I would read straightaway as pertaining to a race track (the non-curved part) and “straight away” as a literal phrase meaning something going directly away from something else (in the right context) or, if not, then a Briton saying right away/immediately. Which is to confirm some of what you said I think.
As a person born in England who’s lived in New Zealand for many years, I would say “She found a job right away” or maybe “She found a job right off the bat”.
Then there’s the Leicestershire version, “straight the way.”
As a 62 year old Briton, I have never heard of the one word version. Obviously, we have “right away” and “immediately”; we just have “straight away” as well. The word order was definitely incorrect in the novel
Tony C’s comment about word order in BrE is correct.
If you combine both versions with “go” or “went” you’ll get interesting results in Ngram.
The word order in that line is definitely weird. “Straight away” and “right away” are both used in British English, and they’re used pretty much the same way as as “right away” is in American English.
“She straightaway found a job” is as weird as “she rightaway found a job” would be in American English.
If you want a one-word version, what’s wrong with ‘straightway’? Although, bizarrely, Collins Dictionary tags it ‘archaic’.
The OED says “now only literary”; the most recent citation is from 1867.
I was amused to see “straightway” just a couple of days ago in the Penguin translation of Sir Gawain and The Green Night.
Two different meanings, I’d say?
“She straightaway found a job” = she immediately went off to find a job and found it.
“She found a job straightaway” = when she went to find a job, the found it immediately.
The pre-adverb is a “time-specifying” adverb (i.e. when the verb was executed)
whereas the post-adverb is a “quality-like” adverb (i.e. how the action panned out, while it was being done).
Compare with this:
“I left the office and quickly had lunch” = I left the office, and not long after that, I had lunch.
“I left the office and had lunch quickly” = I left the office, had lunch, and ate it quickly.
Do you agree with the difference?
Adverb position can be important in general….
“I like you really / I really like you”;
“I alone eat lunch / I eat lunch alone”;
“I often each chips / I eat chips often” (first one suggests “chips as opposed to something else”, whereas second suggests “often as opposed to rarely” – though this one really works via emphasis)…