Originally Posted by
aztimm
I've been to the T5B lounge numerous times and maybe once would I call it crowded
Agree. T5B seems to be less crowded. OP would need to take the train to 5B (an easy ride).
The trick is how to get back to 5A, since FCO flights are most likely departing from 5A. The only way is walking back through the tunnel. There is a post somewhere in FT describing the walk back from 5B to to 5A.