Knitting advice

Thanks for all the advice - I think I should just go out and buy the double knitting wool, that would solve the problem!

I think knitting it in Aran will be too thick. You will need a couple of sizes smaller needles but keep trying the tension square with different sizes until you get it right.

The aran wool will knit up thicker than double knitting.

www.laughinghens.com/knitting-needle-sizes

www.yarnfwd.com/main/tension.html

www.annbuddknits.com/My_Favorite_Formula_v020310.pdf

I don't think in old fashioned needle sizes these days just metric.
If you Google knitting needle conversions or such you should find a solution.

I could try that but what size needles - the ones they suggest for the wool or the ones the pattern dictates?

Could you try knitting up the tension check square to see what size it comes out and adjust your needle size accordingly?