I have done once and would do again, depending on the circumstances. This was to a well known WG with restricted appointments, and a deposit required for new clients. I didn't expect it to be a problem, and it wasn't. If I wanted a WG to make an outcall over a long distance, I would pay travel expenses up front. I'd look at each situation individually, I've hardly ever done so but I don't have a blanket ban as many on UKP do.