Are GP's supposed to offer alternative ways (times) to make appointments?

NoOne

I am classed as disabled due to my mental health. I've had a problem for going on two years now. My GP did some tests for it, and dropped investigations - even thought the problem persists. I had to phone in the morning to make an appointment for the same day to keep investigations going. I have mood disorder and sedating antipsychotics. It's almost impossible to phone the GP at 8pm, if I felt upto it. If I skipped my night time tablets I could, (I'd be awake all night) but that means I might not be in a good shape come the Appointment time (if I got one) and might then put me back to getting up 5pm/6pm and trying for months to get back to a normal ish up at 2pm.

Aren't they obliged by some Law to leave another way open for Appointments that people can access say 3pm 5pm 8pm or something? If so what is the Law called? I'm getting frightened by what's happening and am starting to fear the worst.