So some weight adding tips:
+1 re. brakes, I just got rid of my Gravitas brakes to go back to DA. But I suspect you would be fine with the latest DA pads. Secondly get rid of the Tufo tyres and get some Veloflex. Those will make the bike nicer to ride.
To reduce weight it's pretty simple; make a spreadsheet with current weights, then see how much it costs to save each g. Either set a £/g limit, or just buy things which save maximum g. But I would recommend not going crazy, for instance there is no point in buying light tyres if they give a bad ride (Tufo), don't fit (Schmolke bars and carbon seats) or spending £££s on light parts if you could save a lot more for less by switching to a lighter frame.
Assuming you want to keep the frame and forks I would look at things in roughly this order:
1. Cut off anything unnecessary; seat post, fork, shorten cables, remove stickers, throw away valve caps, shorten chain etc.
2. Focus on the small stuff; bolts, bottle cages, inner tubes, headset compressor and top cap, bar tape and ends, tyres, cables, veloplugs, chain, skewers... There is a lot of weight to be spared there for not too much cash
3. Look at cheaply upgrading the heavier items attached to the frame: saddle, post, bars, stem, pedals
4. Look at lighter groupset items: Cranks and brakes are main weight savers here
5. Change wheels and fork
6. Change frame
I would personally stop after 2. as you will have a nice, well-tuned bike. If you go further you might feel you have a mismatched bike with some areas begging to be upgraded until you spend lots of £££s on a whole new frame, groupset and wheels.