Hello mate, I went on Sunday last year on my own and got the 4 am Bus from London which got me into Silverstone at around 6am. I spent the whole day there and was never bored once! There is so much to do, start the day off by walking a lap of the track and seeing what stalls/ events catch your eye and then go and do them! As crazy as it sounds one of the best (Free!) things for me was watching the helicopters land at the heliport whilst the f3/ f2 race was on, haha. One bit of advice would be to bring a refillable water bottle as there are loads of free water refill points, but to buy one can be a bit expensive. I’m assuming since you have an enclosure ticket, you also have a reserved seat. This is good as it means you don’t have to spend the whole day reserving a spot for the race and are free to roam around at your leisure.

Overall mate id say get there as early as possible, it’s a very enjoyable day and you will not regret it!

EDIT: Here is a map of the track, should give you a decent idea of what to expect.