My concern with sit down stops is waiting for food; any suggestions on places to that aren't likely to involve a long wait?
West End Cafe is the control at Llandovery - at both 147 and 295. The Mariners at New Quay is at 237. The only cause of delay might be if a massive group of bikers get to West End just before you at midday (say). Both places have always seemed pretty swift and the portions generous. In the evening, the BC riders will be the West End's main custom (and they stay open late, specially (so it'd be good to patronise it anyway)).
At New Quay the 'Captain's RV' cafe is another 60m round the corner, if you think the Mariners is too busy (though you need to go into the Mariners anyway). Or before you make the final right down to the promenade:
"R, $ Beach, by Seahorse Inn -
and descend to promenade"
there's a 'Costcutter' store on your left and a pizza place on the right with a few seats.
As I recall nowhere to eat between New Quay and Llandovery.