I noticed this hoverfly yesterday while out at Pelenna yesterday. Following some rather length keying out last night I came to the conclusion that it is Chrysotoxum elegans. Looking at the local records of this species it has been recorded, somewhat irregularly, near the coast so this would represent more of an inland sighting. I don't have much experience with this species and was wondering whether any experts out there could confirm the identity of this hoverfly?
Following a day out with Ian Tew, Tristan Bantock and Ray Wilson we were able to look this hoverfly from the photos I took. The feeling was that the photos don't allow for a definitive identification but that to label this one Chrysotoxum arcuatum cf. was not unreasonable. In fact Ian Tew photographed this species earlier this year, in May, at Afan Argoed on the link below. Some further info in comments. Chrysotoxum arcuatum