One thing to be aware of here, is that the legislation says that you pay this if you own another residential property. What has not be widely publicised, is the fact that if you are married, you are treated as one person for the purpose of these rules. Even if you don't own a residential property and your spouse does, when you buy a property, you will pay the 3% premium.
One further point to note, is that for this purpose, owning another residential property means property worldwide, not just the UK. Therefore, the overseas holiday home does count here, so when you buy a UK property, you will pay the extra 3%.