It lookes like Veronica's choice. I just bought one of these!

Thanks for mentioning another possibility! I've just googled Veronica's Choice and the flowers do seem to have a purplish tinge to them which mine do not. Is yours purplish?
It does look very pretty :)

Mine had only two flowers and both are gone so I cannot confirm the colour right now. But you may be right because my husband recall some of the outer petals of one being off white. Have to wait until the next time it flowers to confirm this. Good luck!

Florida Alba Plena 100%. And how is it doing after 2 years? I have one growing in a shady spot where it gets afternoon sun only and it has been flowering like crazy every year from June till the first frost in November/December. I believe it is not as difficult to grow as people seem to think. Also, I am in zone 6 which is borderline for this clematis.

Sorry for being slow to reply. It was doing really well in its first couple of years but this year it seems to be struggling a little. I'm not sure what the problem is. We did have a very mild winter and it just kept on growing right up until mid-January when a sudden cold snap killed all of its growth. Maybe that has weakened it. Either that or it's getting too crowded.
It's certainly still alive though, and although it only grew a little this spring, it does have a few flowers and is putting out more new growth now.