Llanrhidian marsh road had 1 lesser white throat at the village end, a comm. redstart was singing from some oak trees within farm fields.unfortunately , couldn’t get views of it. Can’t say I’ve heard one singing on Gower before.
At Allt Y Graban, pontlliw , 1 pair of garden warbler both birds sounding slightly agitated. One further singing male further up the road
Glamorgan Bird Club 
I’ve noted a few in the summer on Gower over the years Chris. From memory, Nicholaston / Oxwich / Cefn Bryn foothills area, lots of woods around there. I suppose the odd one or two must occur and probably breed?