If you are installing a door entry system, have the buzzer panel recessed flush with the stonework, not fitted to the surface. It will then be more secure, unobtrusive and less likely to be damaged. If real stone is not an option, use tinted concrete or an epoxy-based screed. Sometimes worn steps can be re-used by turning them over. Tiles or terrazzo finishes are not visually appropriate for West End buildings.
Tiles are particularly prone to cracking.
The Glasgow Conservation Trust West has published a detailed guide to sandstone and its repair as part of the West End Conservation Manual. Please see Stonework for further information. Comments or queries are welcome.