Hi bonitin,
I think it's a strong possibilty that it's Eristalis arbustorum, a 'gravid' female. The white between the abdominal sections is likely expanding due to pregnancy, making them look wider. The triangular marks can be variable in strength of colour, they are just showing the typical shape the female has though.
I think the light shining through the hairs on the eyes is making it look whiter than it is.
Janet