toffee smell from berries of leycestria formosa - why??

Well it isn't toxic but that doesn't mean it would be good to eat.

Yes, my Leycesteria produced the same honey smell from the berries too. I wondered about this myself as well and thought it may be something to do with the sugars in the berries fermenting? Don't know just a thought :-)

Not sure if they are edible Fullbrook. They look designed for bird dispersion. The Caprifoliaceae has some species with edible fruit (Sambucus nigra or Elderberry and Lonicea caerulea or Honeyberry), to others that are not palatable but not harmfull (Symphoricarpos or Snowberry), to others that are toxic to us (most of the climbing section of the genus Lonicera or Honeysuckle).

It is also known as the pheasant bush so maybe they are attracted to it as well ! As you say Fractal to aid seed dispersal