'Ours' meaning 'our home' - where is it used outside the UK, if anywhere?

I didn't know of this usage of ours and yours, so to try and get some data I sifted through lists of hists in two corpora: the British National Corpus and the Corpus of Contemporary American English. I looked for “at ours”, “at yours”, “to ours”, and “to yours”. I went through the hits to check for context in each case. What I see is:

• There are a few results in the British corpus matching your described usage. All of them come from spoken sources (conversations recorded and transcribed), with no such hit from written sources (magazines, fiction or whatever). I would hazard a guess: maybe these few hits are all from a given geographical area or dialect, though I could not confirm it (could not find any detail on the sources in the BNC search interface).
• There is no such usage recorded in the American corpus, which would tend to indicate that it's indeed a regional usage.

That conclusion is not definitive, however, given the relatively low number (a dozen) of matching records in the BNC in the first place. (Absence of evidence not being evidence of absence, unless you have great statistics.) However, that's the best I can do.

There are a number of results in the Corpus of Historical American English (COHA) but most provide context immediately before, e.g.:

"We're always a party, darling, aren't we? You come to mine and I'll come to yours."

Mary McMullen - 'Death by Bequest' (1977)

The query used to generate results was:

• WORD(S): to ours/yours/mine/theirs
• COLLOCATES: back/over/come
• FIELD 3: 4 <- COLLOCATES within 4 word(s) to the left of WORD(S)
• FIELD 4: 0 <- COLLOCATES within 0 word(s) to the left of WORD(S)

As @F'x notes above, such usage may be predominantly found in speech.

However there may still be scope to find additional written examples from this source given the number of possible combininations vs. the limited extent of the query above.

I grew up in New Zealand and my family, who were from the south of England, have always used possessive pronouns like this. So for me saying

1. Let’s go to yours.
2. She’s staying at mine.

is no different from saying

3. I bought it at the grocer’s.
4. I have to go to the doctor’s.

"Come to ours", "go to yours", "pop to John's", "go to my mum's", "a party at Mary's" all work in the same way as "going to the baker's". All widely used in the UK and definitely not a regional variant.

Yet this use is almost unknown the U.S. We hear it in UK television. Particularly in programs from the North. E.g. Happy Valley and Scott and Bailey. Normal usage here is always with the noun attached. my house, my place. Also hear this in reference to siblings and parents. In U.S. Usage is my mother, not our mother, unless two children are present.