Mr Bear. If this is your first time on track I wouldn't worry about all that tyre pressure and suspension setup malarky. The training day with Martin aka HRT is more about rider confidence and machine control. You'll learn how to skid the front wheel and recover. So I would rather spend time making sure how to turn the ABS and traction control off on a GS. The actual flat out time on track is limited as to what you get from say a normal track day. It is still a blast and worth doing. I will miss HRT but they have not done very well in the past few years and Martin is getting old. Pay attention in class, the guy is excellent in relaying his knowledge.
As for bike prep a few guys have given you some advice. Make sure the bike is in good mechanical condition. Take a bit of oil with you, the GS likes to burn a bit nearer the redline. Check tyre pressures before you go on track and tyre condition the week before you go to track, just in case you need a new set. Mirrors and lights don't matter with HRT. If you want to turn the main beam of just unplug it or look
here for a short cut. That is basically all, oh and don't forget to take the panniers off. Handy for taking your kit to track but gets in the way on the corners.
Most important is the rider. He has to be in good condition for the day. Plenty of rest, little or no beer the evening before. Keep yourself hydrated during the day. You wouldn't notice it but it is hard work riding on track. Eat a little at a time and don't stuff it all in come lunchtime. You'll feel sluggish and loose concentration which can spoil your day and maybe the bikes as well. Relax and enjoy the time out on track. It is the safest place you'll ever ride your bike. Have fun you lucky bugger.
Check your kit over. A nice clean helmet is a good start. Smells nice after a wash. A proper fit is essential as most damage done to the body during a crash is to the head, hands and feet because of kit coming off. Take some waterproofs with you. Cadwell Park has its own thing about it.
The place is fantastic and one of my favourites. The only advice I can give you is take care at the Hairpin and Barns when the conditions are iffy, Charlie 2 you cannot see but turn in anyway on the crest from Charlie 1 then aim for the apex when you see it, make sure the bike is in a straight line when you hit the Mountain otherwise it will end in tears depending on how good you are.
Hopefully that mad man will be there on the GSA. David Hallsall is the man's name. A very good and experienced rider. I haven't seen him for a good while.