All sounds very doable Adrian, just because you dont know cars wont make a difference.
At a guess you will have a logical type mentality and understand how things work (even if you need to read up on it first)
Kit options, well your requirements as listed doesnt really eliminate any of them, nor does it highlight any.
I am not sure if DRB still make the live axle version, but this would be the cheapest to build.
But in my opinion, dont buy the cheapest kit you can find and expect it will equate to the cheapest build.
I have an older design Classic Revival
Kobra and found it very easy to assemble, a close second on my list was the Harrison
Cobra Kits: Home I realise these suppliers are a long way from where you live, but I personally think having the supplier close at hand is not that high on the priority list of choosing a supplier.
I have no experiance in a live axle Cobra, but think the IRS cars handle and drive beter.
I am also not a fan of the Jag rear (I think it is only popular because of its ease of fitting) as it is now a very out dated design, the brakes are very hard to service and it is a heavy unit by the time you weigh the assy with the cage.
In saying that though, most suppliers do use the jag rear and it probably the most common assy used and plenty of guys do go fast with it.
Make sure you take a good hard look at the shape, as some do "look like a Cobra" until you know the subtle differences, and to me, the devil is in those little curves.