As stated I am not VAT registered, my last reply has one misgiving and that is for your “EC Sales/Purchases” this adds an additional complication, but with GB leaving the EU this would not be an issue.
In the meantime, perhaps seperate accounts for such purchases under “ebay.co.uk/??” and change the ?? to the EU country VAT abbreviation (to allow for the various VAT rates set around Europe) . OK, this is imperfect, but still less accounts to check!
https://www.gov.uk/online-and-distance-selling-for-businesses/online-selling refer to “terms and conditions”. In respect of purchases made on eBay the terms & conditions are intiated by them with additional terms set for the particular purchase by the the individual seller.
As a buyer on the internet the regulations are written to provide protection. To remove this protection by seperating purchases made through the platform of “eBay” there is a difficulty to refer to the orginator of the action.
Quite a lot of double-shift in all these transactions as mentioned by @Lurch, but the main purpose of keeping our accounts on QuickFile is to keep it simple.