Train.
Parking and traffic will undoubtedly be a pain. Always get the train.
Plus don't you want to have a drink?
I'm not sure whether drinking would be a sensible idea as I normally struggle to get home when I'm in my local area!
Train.
No question
As has been said, just get the train - such a ballache parking in london.
If you're set on driving, check out https://www.parkatmyhouse.com/ to see if there are any cheap spaces nearby - I kind of doubt it, though
I think the event finishes at 3AM, so I'm not really sure on what trains are running around this time, I'll have a look on TFL to find out.