I think thats a plan.
If you've not been to Japfest before here are a few 'pointers':
The police are very active in the area, especially after the event. (small plates beware)
There will be a queue to get in, so allow for it.
For those on track remember helmet, long sleeves and trousers, driving licence (with paper counterpart).
Get noise tested in plenty of time to sort it if your car is too loud.
Go to a briefing (any briefing) ASAP and get it out of the way, otherwise time will run out.
If you've not driven at Castle Combe before take it easy on the first lap - there are no sighting laps!
I think it's going to be dry.