Do you mean for next year? Because sunflowers don't survive the winter?

No. I am potting on a couple of sunflowers in big pots rather than planting them out in the garden, and wanted to no what potting compost would be most suitable?

Right, well multi purpose should be perfectly adequate, unless you want the extra weight of John Innes No. 2 to stop the pots toppling over

Thanks for your help.