The Code of Practice Rights of Access: Goods, Facilities, Services and Premises, outlines what may be considered as reasonable for disabled people to establish rights of access. Several factors can influence the decision regarding whether a change is a reasonable one to make. The extent and nature of any adjustment will depend on the features of the lift and on other factors such as practicality, the extent of disruption, the effectiveness of the adjustment and cost will be taken into consideration. The duty is to make reasonable adjustments, having taken into account all the relevant factors.
As you would expect with installations of this type there are number of standards and regulations of which one needs to be aware, and these will impact on the type of lift that you can specify
A copy of the code of practice can be downloaded from www.drc-gb.org