If you are considering joining as a police officer, the good news is that you are not expected to have a perfect bill of health. The police service does not place a blanket exclusion on certain disabilities/conditions - the Equality Act 2010 (superseding the Disability Discrimination Act) requires that each medical issue should be considered on its merits. That said, a disability or condition that prevents a candidate from undertaking a significant part of the role of police officer is unlikely to be accepted.
We recommend getting in touch with the Recruitment Department of the Force you're interested in joining to discuss your particular disability/condition. Bear in mind that different Forces may interpret the guidelines differently - some Forces may accept medical conditions that others reject.
The following Government webpage may be useful: National recruitment standards - medical standards for police recruitment
There are also many opportunities for joining as a member of police staff, which includes uniform roles such as Police Community Support Officers and Crime Scene Investigators. Most police forces are accredited under the Disability Confident scheme, which means that they actively encourage applications from the disabled community and support career progression for disabled members of staff. Look for the Disability Confident logo on the Force's website.