Its the same with anything, sales tax / import duty / VAT are all different in each country.
If you buy from outside the UK you will have to pay import duty and VAT at UK customs.
Nice explanation John and correct however I think 2Flyer was just voicing his concerns that us UK flyers arnt getting a good deal hence the extra long thread of dissapproval in the UK Phantom group and was so hoping that DJI would adjust their prices. If I do purchase one (no rush atm) it will be when im overseas to avoid this kind of scenario .