Table is done! 12mm Plywood in two sections of 3x4 foot. Piano hinged together. Thanks very much everyone for the advise. I haven't butted it, but it'll be resting on its long face hinged up in this room so it shouldn't bow too much. If it inevitably does I will reenforce it or build a new one by then.

Quick test setup. I will likely position it further towards the wall on the left giving easier and more roomier access to the other three sides. There is a fair bit more room around it than the pictures make out, so it's a nice comfortable success.