Lazy me, I wrote a solution only to realise my output was month-below-month, rather than the required 3x4 table in the example.

Pfffff, and I can't think of a solution to adapt my existing code.

So I'll have to rewrite it.

Sorry to hear that, I hope you get a working solution soon!

reverendbingo (if you're still around and interested in this) -- I think if you change your solution so that it accumulates the output instead of printing it (as I'm guessing it does), you may see some ways around your problem.