Hoverfly (Eristalis horticola)
It took me a fair while to come down on the side of Eristalis horticola and I may still be wrong. However, my book says that horticola is a brighter colour than most of the family and that is true of this insect here. In addition, black 'shadows' on the wings are a feature and it is smaller than most similar species. It is also quite common here in the south.
Taking all those things in to account then Eristalis horticola would seem to fit but if anyone thinks otherwise I would really like to know.