BB, you might be able to save just a few quid if you book online via this: https://www.motorcyclenews.com/news/2018/august/motorcycle-live-2018/ Used this to book mine some weeks back.
and hope your bike's there when you get out. Just a few weeks ago, a bike was stolen from the Birmingham National Motorcycle Museum.
Thats just an open car park! The NEC is inside with full security staff. You go through security and get a wrist band with your vrm on. They only release your bike when you return with the wristband. It's all v safe O Ye of little faith
I used to ride to Earls Court in London from Huddersfield for the bike show. I can't remember the time of year it was then but I certainly won't be riding there from Devils Bridge area this time of year just to save a few quid.
Isn't there a train station or something really close? Sure I seen someone saying park there as it's loads cheaper.
I thought I'd seen something similar too. There is this, but gives no mention of parking (obviously in their self-interest). https://www.motorcyclelive.co.uk/information/travel-parking/