You know, all this time I left the "include vat" box unchecked on the store, assuming it meant that it would leave off the VAT price. Instead, it turns out it means that the vat would be included WITHIN the price if it was checked.
So basically I've been charging VAT all this time and you are the first person who has ever mentioned it! So, thanks for bringing it to my attention! I've gone in and fixed it.
How much was your VAT charge? Email me privately and I'll refund you.
-Dave