I did Nationals for the first time last year, and loved it
I was on the reserve list for all rounds but i managed to get into them all.
Priority does go to people who enter 4 rounds or more of the series and you will need to pay the entry fees up front in full. I started the year as an F5 and now im an F3 and it was my first year doing off road let alone Nationals lol
As for the actual layout of the day, it is a lot more tightly run than i imagined but it works. First thing in the morning starts with a drivers briefing, things to expect through the day, rules, time that you can start generators (if close to housing estates) etc...
First thing in the morning you will have 2 timed practice's in heat order (i think it's 2 anyway
), then straight into round 1. It's your best 2 rounds of qualifying that determine your final and position.
That's the basics really, anything else that you need to know regarding the general rules and more in-depth info can all be found on the BRCA website
Don't know if this is any help lol
shaun.