This is one of those highly sought-after Mexican 'Rose Syringas' with heavily scented waxy nodding bowl-shaped flowers, reddish toward the centre. Almost evergreen, of arching/weeping habit, and not too big, this can be grown against a wall or allowed to grow through other shrubs, as it does in the wild.
Being Mexican and evergreen, this is almost certainly best in a sheltered spot. It has a reputation for not being free flowering in the UK but I've not found this to be the case. In any case it flowers over a much longer period than the more familiar mock oranges, and of course, the scent is wonderful.
Aka P.mexicanus coulteri.
1L pots ~ £7