Well, I've finally gone and done it and weighed all my gear for a 3 day backpack. The total comes to 9.54kg excluding food and water. This doesn't include the clothes I'll actually wear - capilene top, zip-off trousers, boots - fleece, midlayer, waterproofs included in pack weight. Food comes to around 1kg - 2 nights + brekkie, but starting off first day with a hearty breakfast. Plus I'll take 1kg water to start with.
Trouble is, I'll bung in a few crabs, rope and a harness and I'm back up to 20 kg! Bummer!