Hello there,
First of all, my name is Stuart, and I'm quite interested in your project, since I've done similar things before but in raw PHP, but I don't think that it will change much in a WordPress site.
And now, some questions:
* Do you currently have a database to store this info?
* Will this file affect the stock in your database, or just add entries of products?
* What would happen if one of the SKU in the file already exists in your database?
* Are all those columns saved as text or do you have different entities in your database? (Categories, Brands, Colours)
* Why are there 2 "Brand" columns?
* Just to be clear, you want to upload a CSV file, not an Excel file, right? because it will be way more complicated if it's an Excel file.
* How much time will I have to do this? (I ask this because I have my "Real Life Job", so I can't spend more than 4 hours daily on this)
With that said, I'll look forward to work with you, as you can see, I like to have as much as I can clear and setted down before running like a headless chicken into the work.
Cheers ~