aha! after several hours on the internet (*looks pale and tired*) i've found this to be:

Exochorda x macrantha !

according to the bbc website, the RHS gave it an AGM! i can see why, it does have really beautiful flowers. http://www.bbc.co.uk/gardening/plant...ages/310.shtml
now i've identified it, does anyone want any seeds? because i have hundreds.