Obviously a studio needs to have flat access and enough space for a wheelchair user to manoeuvre through it. A set designed entirely within a lowered floor, for example, is unlikely to be accessible unless it can include some sort of shallow ramping. The lay out of the recording space is crucial to the inclusion of disabled people. It is perfectly possible to turn what is, in essence, a fully accessible empty space into an inaccessible one with an ill thought-out set design, or thoughtless placing of cables and equipment. This applies to all studios including the purpose-built professional type. Remember to ask your designer to make access a criterion and that there is flat path through to the seating area.
Every set design must take into consideration the issue of wheelchair spaces. The best arrangement is to have removable seats, so that as many wheelchairs as necessary can be accommodated. Tiered seating usually means wheelchair users are consigned to the front row, but in a small studio with two rows it is possible, in the interests of variety, to ramp the elevated back row as well. A good designer may be able to think of many innovative places for wheelchair users to sit and still provide good sightlines. People who wish to transfer from their chairs, and people with walking difficulties are also going to find it difficult or impossible to use seats that are positioned on a slope, and may also need seats in the front row. You need to keep this in mind on your seating plan.
Health and Safety issues should not be used unreasonably to exclude disabled people. Disabled people should be able, as far as possible, to sit where they like in an auditorium and to attend shows unaccompanied by a non-disabled person. However, some venues have a requirement that disabled people must be accompanied by a non-disabled attendant. If you find the fire regulations in a specific venue do have this requirement, provide someone who can be designated as the 'companion' if necessary.