The legal requirement is to make reasonable adjustments so that disabled people can access your service. Disabled parking bays might or might not be part of that. If you don't have any parking that's suitable for people with poor mobility you might either upgrade it in some way if that's feasible, or if not, provide visiting information that includes somewhere else they could park (eg a suitable public parking bay if one is nearby) or failing that, provide a means of accessing your service that doesn't involve them visiting your building (that all depends on what your service is of course). If there is really nothing you can reasonably do you should just record the justification for that conclusion.

Just an odd thought that few seem to consider - Accessible (aka disabled - improperly nowdays) bays are for blue permit/badge holders only - To hold a blue permit/badge one must fulfill the mobility criteria of not being able to walk more than 100m without rest or walking the distance would impose severe risk to health. This then is a useful guide point. It does make a mockery of much town centre parking arrangements!!

Bob