Insect (365 mono #286)

Anyone know what this is?

Black and yellow striped abdomen and very large.  I am guessing it is a hover-fly, but I didn't know they came in such large sizes.  It was certainly a sinister looking insect, but not as evil looking as a wasp.

Found on a sunflower lead in South Oxfordshire, United Kingdom.

Answers on a postcard please!