Well, July would be perfect for folks in Australia; you probably needn't worry too much either way. ;-) And, yes, there's a line between getting it right and then the sort of procrastinating perfectionism that gets in the way of things actually being finished, and it's not always easy to see which one it is.

What is the thing you're looking to cost? I might even be able to help a bit, depending - I've watched so much 1960s and 70s stuff lately & I do know some cost of living sites, because I'm also interested in social & family history when I'm not being fannish. There are also comms like little_details, britpickery and dw_britglish if you get stuck on small details.