Hi jada,
Checked it with Ian Wallace who confirmed it. He reckons it's one of the first on the wing.
I've got a fair bit of reference work on sedge pupae but not on the adults unfortunately so I checked the Google images which came up with a good page
here where it gives a flight period starting in January. This differs from my FSC caddis guide which gives a summer flight as you say.
Other Google images are dated February, albeit from the Channel Islands so apparently it's not such a rarity as I first thought (for some reason Flickr hyperlinks behave in a very strange way, you have to click the top title to get there)
While on the sedge topic I saw three grannom - the all too forgettably named
Brachycentrus subnubilis on the Teifi yesterday so spring must be coming.