Hi aodsto welcome to the community! :)
1) Technically speaking using company logo's without their permission is a breach of copyright, however it's highly unlikely you'll ever be called up for it. Personally I think its better to be safe and leave the logo's off.
2) VAT is deducted from the total amount of a sale (around 20% I believe), however this only applies to sales made inside Europe. So for example, if someone in America purchases your model, then no VAT is taken. You will not have to pay any additional taxes, unless you start making a substantial amount of money. Different countries have different laws regarding income from royalties, but generally the money made is added to your annual income which is then taxed at the end of each tax year.