LOL. You've got to be kidding.
You would seriously NOT need a car in London.
It's not even worth considering, you'd be absolutely mad. Trust me, no one else will be bringing a car.
All of the halls are in busy areas and central, parking would cost you a fortune and you wouldn't be able to park close to nearly all of the halls anyway. There's a congestion charge Monday-Saturday.
You'd be able to walk or hop on a bus/tube to anywhere you needed to go.