I've been swatching the last couple of days. This seems to be the goer - a smidge over 16 sts and 22 rows to 4 inches on 4.5mm Addi circs. I tried out 5mm bamboo circs first, but it was a tad too loose, and when I teamed the addis with the yarn, they felt like they belonged together (I realise that sounds a bit wacky - sorry).
This isn't the colour I will be using. My LYS didn't have enough of the colour (a tweedy red - with a hint of purple as a dip of the hat to the designer) I wanted in stock, so I will get it next week. This colour is a leftover ball of the same yarn [Patons Jet (70% wool / 30% alpaca)] from a cardigan I knit last winter. The Rowan yarn in the original pattern is just gorgeous, but it's twice the price here and I can't quite justify it in my head.