If you’re dead set on driving, know this: The O2 has 2,000+ parking spaces, but everyone else had the exact same idea. Pre-book your spot online or you’ll pay a stupid amount at the gate. Like, “that concert ticket was cheaper” stupid.
The parking is under the dome, which means you’ll walk through a climate-controlled wonderland of shops and escalators. That’s fine. The problem is leaving. After a gig, the car park becomes a zombie apocalypse of brake lights and beeping horns. Give yourself 45 minutes just to exit the building. Seriously.
Don’t even think about parking on nearby streets. They are either residents-only or will tow your car so fast you’ll think it learned to teleport. Stick to the official lot.