New Business & Book-keeping Questions

Total 'newbie' here. Thank you for being gentle as this is my first post!

My father user to keep my books when I was last self-employed. He used a Simplex D book and always managed my finances for me. But I knew that I was not going to gain any bookkeeping experience whatsoever that way. So now, here I am, back in self-employment and effectively starting to learn the ropes all over again. Very sadly, my father is no longer around to help, so time to stand on my own two feet!

My crafting skills are good! But my numerical skills leave a lot to be desired, My little crafting businesses are very straight-forward. I sell my own hand-made products in online stores. At this stage, I don't see the need to create over-complicated accounts with detailed profit and loss forecasts, etc. so I want to keep my bookkeeping as simple as possible, including only the date of a transaction, the person or company concerned and the amount. I will be using Libe Office Calc for my bookkeeping.

I know that bookkeeping is a simple matter of keeping records of how much money comes into the business and how much goes out. I have searched this site and found lots of valuable information, however, I still have a few questions. Any help would be gratefully appreciated.

Regarding money received in my online stores: Customers make a purchase and I see the gross amount, less the seller fees. Only the nett amount goes into my bank. How would I account for this correctly? Do I include the nett amount as that is all my bank account will see? Or do I need to list the total payment and the seller fee separately? It's a small point, and maybe I could use that fee as an offset for tax purposes?

A simpler way to do this would be to enter only the weekly "Funds sent to your bank account" amount, lumping all the week's sales together. Please don't tell me I have to list each sale, the listing number, the address of the customer, etc. It will take for ever!

Regarding fuel costs, how do I account for this? Just include a weekly mileage figure? I have to travel to buy stock, sometimes 200 mile round trips. I had a 160 mile round trip to buy stock the other day and this works out at £72 allowances. That seems a lot to me when I only put £20 of diesel in my car. I don't understand what I am to do with this.

I believe you can have up to £4 per day meal allowance too if you are on the road for your business? Is this correct? How do I account for this in my bookkeeping?

Sorry, probably very simple questions, but this fills me with dread!