It means that lawyers have a format that they can use if a person of Islamic faith wants a will drawn up in accordance with their wishes -- and gives some legal formats for their wishes being upheld.

It doesn't mean that Great Britain's laws are going to be changed to conform or that all wills will conform to that or that non-Islamic wills will be able to do this. Not that it's entirely unusual -- people have wills of this kind everywhere and have -- well, ever since there were written instructions for "who gets the silverware after I die."