Thats all pretty solid advice! Ive built 3/4 bikes in the last few years.
The best cash you can spend is on a comprehensive set of tools – you may already have them – I got a basic kit for @£70, and a work stand.
For the following big ticket items I would get:
Forks – RS Revs 150 from merlin @£300
Brakes – Deores from Rose @£70
Wheels – Classifieds @£200 for a TLR/UST set on Hope Pro2
Groupset – SLX from Actionsports.de – mine was @£200
Dropper post – ICE LIFT V8 from Purebike.fr for£87 posted
Stem/Bars/Grips/Seatpost/Headset – Superstar/On-One Should get you what you need on the cheap.
For S/H components, try Flatoutcycles.co.uk. Little things like QR’s are quite good from there.