I had a beautiful Choiysa ternata Mexican Orange Blossom) in Bucks for many years and although, I sort of agree with you, pete, the leaves don't look right and look more like that of a Deutzia gracilis which has more slender leaves that the C ternata. I think the telling thing would be that when the leaves of the Choisya are crushed they are fragrant ... I don't know if the Deutzia does as I have not had one.
I think there is another one called Goldfingers which is a cross between Sundance and Aztec Pearl, the Dutch have another couple called Moonsleeeper and Brica, not sure about their parentage.
