This has been covered before, when we went down to Chepstow last year, we saw quite a few z's and none waved, I just wave and and flash and believe that I'm the happy chappie and their the sad buggers
On the English Welsh meet, there where loads of Z4's and none waved
Although I did get a wave from a Z3 owner near Tintern 
On the English Welsh meet, there where loads of Z4's and none waved
Although I did get a wave from a Z3 owner near Tintern 