Sorry it's a bit long and link-heavy,but...
Don't place too much emphasis on jigs, they don't guarantee a straight frame or make your job much easier, just something to hold the tubes in place and act as a reference. Some of the really good jigs (Henry James, Anvil etc $5000+) are brilliant for more serious production. However, any of the frame fabrication methods will distort joints and mess up any alignment from even the best jig. Without very careful sequencing and care, pretty much every joint will need re-setting, by torch or 'cold setting', especially when you're starting out. Some UK builders (Jack Taylor, Hetchins, Higgins, Thanet etc) built entirely on a hearth without jigs, just referring to a full scale drawing and plumblines, straightedges, string and spirit levels for alignment. For an internet blog version, see Suzy Jackson's Little Fish site
As for the £1000 cost of a course...If you seriously want to build yourself a frame on your own, it's going to cost more than that in materials, lugs, specialist tools, Oxy Acetlyene kit, gas accounts, benches, drills, half round files, riffler files, saws, bench grinders, abrasives, reamers, dies, taps etc etc.
Considerably better than YouTube, but a lot cheaper than a course, look to Tim Paterek
. He's a very experienced Minnesota builder who has trained many framebuilders, and ran courses in the past. He publishes a set of manuals and DVDs...I'd rather you bought it from him to support the cause, but I do have a copy of Tim Paterek's Framebuilding Manual in hardcopy and pdf, which I'd lend. It's an early edition from about 1989, but it's all still relevant for steel building, lugged and lugless, step by step, with drawings for fixtures and jigs etc.
Don't just buy a tubeset (fairly pricey actually) off eBay and busk it...look at the range of tools, parts and tubes available from Peter Evans at Ceeway
(who also sells lug 2nds for £1 each for practicing), Nova Cycles
, Paragon Machineworks
, Kirk Pacenti
, Hank Folson
They're all very friendly, and only too happy to help out a beginner.
Read as many opinions on geometry and fitting as you can find (there are hundreds out there), try the apps (SizeMyBike etc), try out Rattle CAD
. Do the homework, browse the framebuilders' sites listed at Richard Sachs
Finally, I've got a 1" headset/27.2mm seatpin/68mm BSA BB front triangle jig (ex- Dennis Hill, Hill Special in Lancs.) that hasn't been used for 10 yrs. along with plenty of frame parts. I'm more than willing to lend to an aspiring builder, perhaps after attending a course. I certainly wouldn't want to ride something made using instructions off YouTube. Seriously, while technically it is
just fancy plumbing, you could die...
PM if interested.
Pause, take a breath and ask yourself: "What would Rastamouse