yes it is a female Syrphus, this genus is very hard and many pix of females and most pix of males are not IDable, even by the top experts, but yours *seems* to be Syrphus ribesii as what can be seen of the hind femur is yellow. In the females of the other common british species it is mostly black, although the distal end is yellow. I wouldn't be 100% sure however as you don't have an unobstructed view of the whole length of either femur.
cheers,
James