They don't charge VAT because they are based in the Channel Islands and there's no carriage charges either. Be careful when comparing prices though as there appear to be different capacity ink cartridges available.
When you ave found a good supplier, consider installing Inksave which allows you to make up to 75% savings on ink usage. A free trial can be downloaded or software can be purchased from Amazon for about �20. I have used it now for about 18 months, to my advantage.