1) 240V, more amps the better, if you are going to go big discuss it with an electrician. Get him to put in a sub board and think of future capacity.

2) will ur internet work if your local exchange has no power? If not its a waste of money, but is probably not cost effective anyway.
sorry read pdu as ups   do you need a psu (maybe this is a us term am not familiar with as i have read it a few times recently) will normal sockets not be enough? make sure they have an RCD and think of a sub board for protection.

3) If you are handy with a soldering iron and noice is not an issue I would go with modding server supplies, theirs a few threads about them here already, I would recommend 1 per Ant for redundncy as there really cheap anyhow.

4) Any that has enough depth + a bit, mine is a little short. Wire racking will allow better air flow but is conductive so take extra care.

Additional

If your having new line installed get the electrician to install an isolator near the door, its relatively cheap initially and will provide quick isolation should you have problems.

Put a CO2 extinguisher near the door.