I have raggy throwovers and a tank bag when I'm away on the FZ (pics from Farmyard on my profile) expandable and can carry loads, just be careful with tank bag, plastic tank on CBR innit, secure proper and don't load too high you might want to see clocks and don't forget to fill up before putting it on . You say you're doing DAS in May so will come in handy as starter on big bike.
Get a lightweight tent, a large waterproof sack (you can buy 'em with handles on!) and some bungees. Alternatively use a rucksack and some bungees ... Old School stylee! I would have thought trying to get panniers/throwovers off the bike and to camping field at Download would be worse than sticking a rucksack on ya back! ('cos there aint a cat in hell's chance of your bike getting within spitting distance of the camping). It's a helluva walk... IMO Worth it though ;) Enjoy yourself. No Download for me this year, going to HellFest (YAY!) :D
The throw overs look good Old Red that's some load you had on there, think I'll have to nip to J &S see what's available and then bungee (Old School stylee lol) everything else, just need something lightweight that can hold a decent amount.