Cuckoo Spit.

Another in my "walk to the bins" series.  I have always known this as "Cuckoo Spit", even the RHS calls it Cuckoo Spit.  Despite the name, it has nothing to do with Cuckoos.  The froth is developed by the Nymph of a sapsucking bug.  The name probably came from the fact they generally appear at the same time as Cuckoos.

There are 9 species of Froghopper in the UK, this is likely to be the "Common Froghopper" which isn't choosy about the plant it feeds on, in this case, Lavender.  

Long term there is a worry about if the bacteria Xylella fastidiosa ever arrives in this country.  The bacteria is spread by sapsucking insects, causing many symptoms including, wilt, dieback, and sometimes death.  Fortunately, it is no nearer than southern Europe, where it is causing serious problems.