Hi Phil,
Dinas RSPB is a great place to visit, Dippers along the river, Red Grouse on the hilltops and a very scenic drive aswell.
Elan Valley is another great place with reservoir after reservoir. These could hold Goosander and Goldeneye with Hen Harriers patrolling the grasslands.
The coast is only an hour away where small colonies of Choughs are present, Llangranog beach is a favoured spot for me.
Ynis-hir is a lovely reserve to the west of Tregaron, White-fronted Geese, numerous Waders, all 3 Woodpeckers.
Last but not least is Cors Caron Bog right next to Tregaron. Whooper Swans winter here, you might just be in time.
Hope this helps
Matt