[Syrphidae] Migrant Syrphidae in Eire/British Isles?

[James Alan Wolstencroft]

Dear All, 

To what extent is it known (or 'supposed') whether Helophilus spp are long distance migrants e.g. in or to Eire/BI?
I was on a thrift covered cliff-top, on westernmost Dursey Island, off westernmost Cork, last week and noticed an apparent arrival of Helophilus in association with relatively small numbers of various migrant Lepidoptera.
No Episyrphus balteatus however, and few Eristalis spp.

Many thanks,
JW