Ben,
I would recommend leaving next Wednesday.
If that isn't feasible, albeit reasonable, then as soon as possible thereafter. People generally start arriving on the Sunday, athough the ACO charge an extra few bobs for early arrivals. About 7 Euros I think. There are qualifying sessions on Tuesday/Wednesday/Thursday.
Having said all that, things are due to change next year, and pre-qualifying is starting on the previous weekend, so I'm not sure what the arrangements will be.
In fact, basically, I know Jack Sh*t, and am sorry to have wasted your time. I'm not even sure what my mother looks like and am wearing odd coloured slip-ons. There's a bloke at the bottom of my street crosses the road when he sees me approaching, and I'm not sure why either.
For chrissakes, someone here will know though. Will you tell me? Please.
H