Hi,
I'm giving you this information on the understanding that I am not a lawyer, disability rights person, etc. I am just interested in the rights of people with disabilities. These are my interpretations of the Act only.
If you look at the act (link below) it gives detailed info.
Disability Discrimination Act 1995 (c. 50)
The parts that would particularly apply to you, I think, are as follows.
PART III
Discrimination in Other Areas
Goods, facilities and services
19 Discrimination in relation to goods, facilities and services (1) It is unlawful for a provider of services to discriminate against a disabled person—
(a) in refusing to provide, or deliberately not providing, to the disabled person any service which he provides, or is prepared to provide, to members of the public;
(In other works, you can't just say - Sorry, you're disabled. I'm not going to treat you.)
21 Duty of providers of services to make adjustments (1) Where a provider of services has a practice, policy or procedure which makes it impossible or unreasonably difficult for disabled persons to make use of a service which he provides, or is prepared to provide, to other members of the public, it is his duty to take such steps as it is reasonable, in all the circumstances of the case, for him to have to take in order to change that practice, policy or procedure so that it no longer has that effect.
(2) Where a physical feature (for example, one arising from the design or construction of a building or the approach or access to premises) makes it impossible or unreasonably difficult for disabled persons to make use of such a service, it is the duty of the provider of that service to take such steps as it is reasonable, in all the circumstances of the case, for him to have to take in order to—
(a) remove the feature;
(b) alter it so that it no longer has that effect;
(c) provide a reasonable means of avoiding the feature; or
(d) provide a reasonable alternative method of making the service in question available to disabled persons.
(This means that you should try to provide the service by other means if possible, e.g. offering to visit their home if this is practicable for you, or allowing them to have the treatment in a downstairs room, again if practicable ie not lugging treatment couches downstairs as this can cause you injury.)
As the stairs are in your home, you wouldn't be expected to put in a lift, etc. If you offered one of the above work arounds, you would be fullfilling your obligations under the act. Not sure what would happen if you didn't want to offer these to a disabled person if they asked. Probably nothing, as other areas in the home are used by family members and I wouldn't think you would be expected to make an area a "temporary salon" for the duration of their treatment.
Hope this helps, and remember these are just my opinions!
Marion X