Section 20 of the Equality Act 2010 imposes a duty on all employers to make reasonable adjustments to any provision, criterion or practice applied by them, or physical feature of their premises, that places a disabled person at a substantial disadvantage. The Equality Act 2010: employment statutory code of practice (PDF format, 1.09MB) (on the EHRC website) lists examples of steps that an employer may have to take in order to comply with this duty. The examples given include "allowing the person to be absent during working or training hours for rehabilitation, assessment or treatment". However, the code says nothing about payment for such time off. What is reasonable for the employer to do will depend on the circumstances of the particular case.
Relevant factors to consider will be the employer's size and financial resources, the terms of the employee's contract, whether or not the employer normally pays employees for time off work to attend medical appointments (and for time off for other reasons such as sickness absence), the amount of time off that the disabled employee requires and the cost of paying for the time off. In essence, unless there is some tangible and concrete reason why it would not be reasonable to pay the disabled employee for time off to attend medical appointments, payment should be made. Even if it is not the employer's normal practice to pay employees who take time off to attend medical appointments, it may be reasonable to make payment in the case of an employee with a disability. Section 13(3) of the Equality Act 2010 makes it clear that it is not discriminatory against other employees to give special treatment to a disabled employee.