Advice on where to start I've seen this (http://petapixel.com/2013/04/12/check-out-this-lego-slr-and-its-lego-camera-strap-and-lego-strobe/) and really want to build it but cannot find instructions anywhere.

I can see the obvious parts but where on earth would I start with the bits that are well hidden away? Has anyone got any ideas of how it could be done? Is it just a case of playing around and seeing or can someone provide elusive instructions that I've not been able to find. Before you ask, yes I have contacted the designer to no avail.

I don't have enough of the right colours to be able to play but guessing software can do that but does that produce a list of bricks I can then buy? Not played with it before.
I do not have much specific advice for the building of the model, but to get the pieces to physically create it, I can help with.

BrickLink will be the superior tool for you to be able to create this model yourself, and then buy the pieces for it. If you don't already have a BrickLink account, you can make one at this link:
Bricklink Registration

Stud.io Download
Once you have done so, click the above link and download their beta program "stud.io" which is a brick-building software that is very similar to Lego Digital Designer (a program originally released by TLG). It is more compatible with BrickLink than LDD, and you can link your BL account to stud.io.

Once you build a model in stud.io, you can easily upload it as a 'wanted-list' to your BL account that includes all the parts you need for your model that you created in stud.io. You can follow the steps on BL to get your parts in the most convenient fashion. I have found this to be cheaper and quicker than any other alternative (unless, of course, you have a massive collection of Lego pieces).

I hope that helps.