It may not sound fair to you, but your employer is going beyond its statutory duties in protecting your pay. Its only duty in this matter is to seek to accommodate you, in the light of your injury or disability, by making adaptations to your working environment or to your job. Some employers stop here and say that they cannot show flexibility in this way. It is not obliged to ensure that the pay remains the same, but has decided to give you some protection in that area. To find out more, you could speak to your local branch of Acas - listed in the telephone directory.
Answers are for guidance only.