Have just spent a great week at Pandy cottage. Off the beaten track, but close enough to Lampeter for all your requirements.
Everything you would need for self-catering is on hand in the cottage plus more. Very comfortable sofas and double bed, lots of space for two people plus a dog. Lovely garden plus a huge enclosed field to potter around in.
Great welcome of fresh bread and home-produced honey, fresh flowers and a little of everything in the cupboards to get you started.
Great centre for a week's walking. Within an hour's drive there are beach walks, mountain walks, historic sites, nature activities. Maps are available in the cottage both for the locality and further afield.
We wouldn't hesitate to return to Pandy cottage for another holiday in the UK.