That's a quick bike you've got there and Silverstone is a very wide track so it could be forgiving or it could be really dangerous because you're going to carry some real high speed into some of them corners.
The thing is about trackdays and it's easy to get focused on relative speed and pace, is that it's to be enjoyed, and it is very different from road riding (at least my road riding). First trackday just enjoy it. Don't worry about pace just learn the lines, relearn them and relearn them as you get a bit quicker each time. Go out determined not to be the one to crash (there will be crashes).
I have a mate, a "fast road rider" who froze on the track, couldn't handle the noise, atmosphere or there being faster bikes buzzing past him. He bottled it big time.
Tyres? Dunno what you have but a think about a pro riding your bike and your tyres, he'll blitz you easy. If you ride well you won't out perform your tyres.
Go in novices, try to enjoy it, plenty of time to move up as you do more.
My 2p worth. Good luck (Doningtons better
)
Edit: oh yeah some novices are real slow but the videos always make it seem slower than it is.