Hey PapaC - I'm not familiar with the sites that you mentioned, but I don't think that Pokerstars
(play money games) can be beat for free play. I'm trying to develop my multi-table cash game skills, and find that 4 to 6 Stars tables are super easy to start up in a few seconds with their "Quick Seat" feature.
Now you may argue that the competition offered at play money table tables just isn't the same as real money tables, and I would definitely agree. That said there is some pretty loose play at real money tables too. But it's still a great way to practice monitoring and reacting to play on a number of tables at the the same time.