http://www.equalityhumanrights.com/uplo ... bility.pdfhttp://www.direct.gov.uk/en/DisabledPeo ... DG_4001068
That PDF lists Fibro as an example of a condition which MAY be disabling. The only conditions considered to be automatically a disability are Cancer, Multiple Sclerosis and HIV/AIDS.
Other conditions can be considered disabling:
In the Act, a person has a disability if:
•they have a physical or mental impairment
•the impairment has a substantial and long-term adverse effect on their ability to perform normal day-to-day activities
So for many people Fibro will fit that description if it means they struggle to shower/bathe, cook, walk, sit for long periods, use a computer for long periods, difficulty concentrating etc.
I doubt your employer will request specific detail, but just be aware of how you can demonstrate Fibro meets the criteria just in case they do ask. They probably won't ask though. I hope you can get evening shifts if that helps you