Just phoned them to book a car parking space as per the website but the guy just said turn up on the day and pay, I was thinking they would take my reg plate, its just we are going to be pushing it for time getting down so don't want to arrive around 7.30 to be told no space and then have to hunt around looking elsewhere for a space.
I'd say you'd be struggling there pal, I'd try Canon's Park tube station, it's only a few stops from Wembley Park - you'd probably want to make it about 6pm though, after the commuters have taken their cars and before the football traffic arrives.
I've payed to park at Chalkhill primary school before for a few England games. About 10 minute walk to Stadium
I always park at Ruislip and jump on the tube. Trains seem to run every 8 minutes or so and it's about 20 minutes into Wembley Park. It's pretty easy to get to and from Ruislip from the M25.