First of please accept gratitude 
for writing such an elaborate and excellent article. Through this article many of my doubts are clear and I am a fan already. However :
I have a question. I am working on a website on which a particular kind of items will be sold. For which I am currently contacting companies. The buyer will be making a payment on my website. I will be taking payment on behalf of the companies that will be selling on my platform, after deducting my commission from the entire amount I will forward the entire amount to the companies. In that case, I will be generating an invoice on behalf of companies in my name for the buyer of the product, so will it still be part of my turnover or just the service that I am providing will be part of my turnover. Because I am not buying anything from the company, I will be just providing them a platform to sell. Kindly advice on the same, also how will VAT work, on the service or the entire Invoice of the good sold? I know it is a mind-boggling question but it will help me a lot
Thankful.