Last year on my hols to the Dordogne I took the liberty of helping myself to one of the sunflowers that had matured to seed heads in the fields next to the property we were renting. They were giants - but I have no idea what they are, other than sunflowrers, or whether they are likely to be okay in the UK.
Anybody who can help me - or do I just grow them this year to see how they do?
Plant them and see. Don't put them in too early.