To be honest that figure represents just over a 50% saving from what you've quoted further up the thread. That sort of saving is reliably achievable by buying bikes from a year or two previously from large retailers such as
CRC etc. I bought a 2011 mtb from them this summer for £1350 and the equivalent bike for 2013 retails at £3199.
If you've not got a good background in maintaining bikes then building one from scratch specifically to save money is usually a recipe for disaster. So far the cost is £100 (wheels and frame, shifters) factor in fork, headset, cables, brakes, drivechain, bars, tape, stem, seatpost, saddle, tools etc and the costs start spiralling. You've only got to take a quick look through ebay, bikeradar, pinkbike, gumtree etc and you can pick up a decent bike for 2-300 quid.
My advice would be buy secondhand and learn how to maintain it as you go if you want to save money.
While self building is achieveable, there's a lot of common sense and previously untouched points above.
First thing i thought reading OPs opening post was, crankset, fork, brakes etc etc etc ? are any of these parts included ? Sourcing them all adds up, i know, ive done it and while you can save money, it doesnt come cheap.
Do the shifter come with cables and outers ?...not cheap items.
Brake calipers, perhaps £15 to £20 second hand.
I assume forks are included.
Crankset, BB, seatpost, saddle, handlebars, tape, stem, even little stuff like downtube adjusters, you really need to know whats is, or isnt included to know whether its a financially sensible project.
Put it this way, i was selling my Via Nirone C2C Xenon last year, new wheels (albeit budget Rodis), new tyres and innertubes, new bartape, newish rear hanger, upgraded BB, a well used but well maintained commuter for £230. I wasnt overun with buyers which tells me it was too expensive or perhaps the wrong time of year.
Not trying to put you off, rather letting you know the hidden costs.