That story was a newspaper lie. Such weapons can only be held in the uk if the automatic fire capability had been removed and then only by a person with the highest class of firearms certificate. They CAN NOT hold the weapon at home , it has to be kept and used only at a special shooting range.
If you read the artical it says that a gun ' Based on' the one used in the USA can be sold in the UK. This version is a single shot weapon NOT a fully automatic one but it is based on the US gun. Anyone wanting to buy it would need a Class 1 firearms certificate these are now almost impossible to get apart from people like police firearms officers or armed forces training experts, and they would need to show where it was to be kept and used.