Update:

The Behringer C-3 is great. It works very well when all players are sitting quite tightly together. As must be expected though, once we get so crowded that some players have to sit too far "off mic" then it is of no benefit to those players.

Feedback does happen, but it's manageable - even with just a PA speaker and no notch filter. It's all down to positioning, controlling volume and rolling off the bass frequencies a little on the powered speaker or on the mixer.

We keep the volume really quite low. The aim is just to help the sound make it around the L-shaped corner, not to make us loud.

I'm pretty satisfied, and I can recommend the Behringer C-3 as a good value mic.