I found this hoverfly buzzing around the kitchen window today. I've keyed it out a Criorhina berberina. Stubbs mentions that all the Criorhina are scarce but this species is the most common of them. A few records on the NBN gateway database show it to be infrequent in Glamorgan, records coming mainly from the Gower. Ian Morgan's Notes on the Status of Hoverflies in Carmarthenshire (available online here) show it to be in five 10km squares from that area. It can be a feature of ancient broadleaved woodlands, which in the case of this record is provide by the Gnoll CP.