Or Stanmore. That's where I park for away games in London, there's a Tesco where you can park all day for £6 or something, secure and all that.
Boardwalk shopping centre Edgeware £2 per day and if you lweave on a sunday then its free no matter how long you have been there!! right next to the last stop on noerthern line and 2 mins from J4(i think) of M1
Park up outside mine if you like Dave, nice road in Highgate N6. Just off A1 Archway road and 3 minutes from Highgate station.