Plant ID please This plant is growing in my neighbour's garden

At that height some sort of sunflower??

It is Rudbeckia lacinata probably one of the varieties of the double forms of hortensia. they grow 5-10ft tall so fits in with this. it is a stunner. I will certainly add this to my wants list.

Or is is one of the double forms of Helianthus, perennial Sunflowers?

My first thought was Rudbeckia laciniata 'Hortensia' but the leaves are wrong. The leaves look more like a Helianthus but which one?

I think you're right about Rudbeckia laciniata 'Hortensia'. I think those leaves belong to something else - there is one rudbeckia leaf in the top right corner, lol.

Helianthus. x. multiflorus. But there are named forms of this and it could be one of them.

Thanks very much for all your help