Hi Kate - Woo you leave the easiest question till last !
Sorry not enough space here but, to summarise, goods or services you buy in that don't carry VAT will fall into 4 categories, Zero Rated, Exempt, Bought from a non VAT registered businesses and "Out of scope".
The general rule is that only the last category should be left out of the VAT return by picking the Exclude rate or "Out of scope" treatment, all others are recorded using 0% VAT and one of the other treatments.
There are exemptions to this general rule but most people don't need to worry about them, so all you have to do is identify out of scope expenses and exclude them from the return. Your drawings/personal items are a typical example but for a list have a look at section 3.8 of this guide for items not to include in Box 7 of the return:
https://www.gov.uk/government/publications/vat-notice-70012-filling-in-your-vat-return/vat-notice-70012-filling-in-your-vat-return#section3