Why do you charge VAT to International Customers?

VAT, Customs & Excise HMRC Reference: Notice 741A (January 2010), If you supply services that relate to land or property, the place of supply of those services is where the land itself is located, irrespective of where you or your customer belong.

http://customs.hmrc.gov.uk/channelsPortalWebApp/channelsPortalWebApp.portal?_nfpb=true&_pageLabel=pageLibrary_ShowContent&id=HMCE_PROD1_029955&propertyType=document

Currently the VAT rate in the UK is 20%, and the good news is the VAT can be claimed back in full at your end.