Thanks everyone! Didn't think I'd get so many replies in a day. Let's start addressing...
Sleeping bag - I'm using Overland Track Transport to get myself from Launceston to Cradle. They provide gear hire - S2S down bag, just over 1 kg.
Gaiters - keeping them.
Base layers - losing one pair of legs, one shirt, and the singlet. Just one set for the trip.
Mid layer - losing merino jumper.
Outer layer - Considering losing the rain pants. I think I can get by on just shorts and gaiters...but still unsure just in case the rain and wind chill my thighs pretty good.
Zip ties - I've read that the birds like to try and get into your pack when you leave them for side trips and to zip tie the zippers to stop them. Is this true? For the minimal weight I think it would be good to reduce the risk of losing food.
Water bottle - dropping macpac bottle for the cheap plastic bottle
Phone charger - plan is to stay at friend's in sydney before flying out to launceston in the morning, then stay a day in launceston for last minute stuff, then bus the next day to Ronnys Creek. After I'm done I'm meeting my wife and daughter in Hobart. So there'll be some time when I need to use my phone. Hopefully I can just get by with the powerbank. My phone doesn't allow me to swap batteries.
Camera - I'm also one of those people who enjoys taking pictures, so it's coming along. Although I'm an ultra-amateur! Hence the spare battery if I'm endlessly trying to find the right exposure settings

Cooking - I'll stick with the whisperlite. Not 100% sure the 650mL bottle is enough for 7 breakfasts and dinners. Can hire a 1L bottle if needed. More on food later...
Pack - stuck with this one for now
Headlamnp - I've got a BD storm. Will lose the extra batteries.
Thongs - keeping. I do enjoy letting my feet breathe.
Underwear - I have a pair of skins I use for other sports. Might also invest in a pair of icebreakers.
Footprint - only reason for bringing this along is I plan on spending a night or two (weather permitting) around the labyrinth, acropolis, lake elysia. Sounds like my tent will be ok without it if I'm careful where I place it.
Day pack - will swap for the S2S packable bag. Minimal cost for good weight savings.
Passport - thought I might need it for the flight...guess not!
Toilet paper - I just weighed a full roll...3 ply! Will reduce the size of this.
Towel - may swap for a S2S drylite
Food - here's my plan so far (and it's the last bit of planning and prep I've done):
Self made, three types of trail mix, switching each day for varierty. Total 2.2kg (yes, this will be my snack on trail and lunch most days!)
Breakfast is 7 days of 150g oats, with berries and/or sweet spices. Coffee. Total 1.2kg
Dinner is strive food for 5 nights and some tuna pasta 2 nights. Total ~1kg
Other snacks & energy food - 200g beef jerky, 200g chocolate, anything else I impulse buy in Launceston! Total ~0.5kg.
So total has been revised to an estimate of 5kg.
Revised overall total is about 20.2kg! I can reduce this another ~0.2kg if I swap dry bags for a pack liner - still undecided on that one.
Guess I'll see what works and how my body feels in 3 weeks!
Thanks everyone for the assistance!