I suspect what we call Song Circles in the States are very different from Sessions across the pond.
It would be unspeakably rude to criticise someone's performance at one of our Maine song circles. We are there to share the music and enjoy each other's contribution.
If, however, you choose to perform at a festival for example or on stage at a coffee shop and you screw up - you're on your own.
Someplace like the Getaway is also very open to different levels of talent. It is a real thrill to sing a song as best you can and have a "famous folkie" ask for the lyrics.
SINS