I think Lindisfarne's first couple of albums are pretty good for what they are
Sure, they're a bit on the cheesy side at times and I typically like my English folk either more traditional (a la Shirley Collins) or more rockin (a la Fairport) and Lindisfarne's sorta halfway between the 2. But the songwriting is pretty good- they definitely know their way around a catchy melody. Haven't listened to any of the later stuff though so maybe they do get terrible as you say.
Never checked out Poco but have always been curious because of the of Furay's involvement, as I always liked his songs with Buffalo Springfield, even if they generally couldn't really touch Young's or Stills's.