I'm seeing weights around 1750-Can't remember any of the weights from when I bought mine, but the stock wheels/tyres were considerably heavier than the Open Pros I had built on Hope rear/shimano dyanamo front. A lot of this weight is in the stock tyres though.
1900 g. I guess that the standard wheels must be in this range. Maybe Shimano XT/Mavic open pro would be a good quality, but cheaper alternative to Hope?
I'm thinking 105 compact chainset, 105 mechs and shifters with Avid BB7 brakes. No idea about bars and stems, but Ribble seem to have good prices for road stuff.
I've got on very well with the Tiagra drivetrain. My bike gets used everyday (quite a bit off road) and not cleaned that often so I would be loathe to grind away expensive bits when I can get away with less. That said, I did replace the rear mech with an MTB one (as Keith said above, when you have dual panniers filled with shopping it gets very heavy!)
I have gradually replaced other bits and bobs on the bike though. CRC were doing Easton EC70 carbon posts in the correct size at a good price recently (they might still have some). I picked up some Easton EC90 bars from Merlin (I think) when they were half price, which I can recommend.
Would definitely recommend a Brooks (or SJS equivalent) saddle - dead comfy, looks great with the style of the bike. Obviously weight not a real issue with this sort of bike.
BB7s are OK but I replaced them fairly quickly with Hope V-Twin. Having said that if you do want BB7s I have a set in my spares cupboard with probably only a couple of hundred miles on them that came off my Croix de Fer...
oh yeah and SKS Chromoplast mudguards look & fit great (with a bit of fiddling!) and I would recommend them too.