Forgive my ignorance, but I've only been an amateur emtomologist for two weeks! Been on sunny Wimbledon Common taking a few snaps of chaps, and I reckon this is Syrphus ribesii, it certainly looks like that in one of my guides. However Chinery pictures it without the divided eyes and says face has no black line (if I'm correct in equating these these pieces of information). Did I read somewhere else that the divided / non-divided eyes were male / female characters in Volucella zonaria or am I totally up the wrong bramble.
You are right on all counts: males (usually) have contiguous eyes, females always separated. The species you have indeed appears to be Syrphus ribesii but there are two closely related species and the fact that you chose the correct one is close to sheer luck. The combination of it being a female (separated eyes) and the hind legs being all yellow gives a positive ID for that species. The females of the other two species have black hind femora (the first large part of the hind leg that just protrudes from under the abdomen).
The three Syrphus species:
Syprhus torvus: eye are shortly haired (not particularly dense but generally well visible against the correct background)
Syrphus ribesii: Female: hind legs with all yellow hind femora; male; hind femora black, except at tip: the yellow part has small black hairs (magnifyr!)
Syrphus vitripennis: Female and male: hind femora black, except at tip: the yellow part has small yellow hairs (magnify!).
Whether these are 'obvious' characters? Well that depends on your power of observation or the skill of your photography.